AU2007248156A1

AU2007248156A1 - Passive phonography heart monitor

Info

Publication number: AU2007248156A1
Application number: AU2007248156A
Authority: AU
Inventors: Nicholas P. Orenstein; Ezra J. Rapoport
Original assignee: Lono Medical Systems LLC
Current assignee: Lono Medical Systems LLC
Priority date: 2006-05-02
Filing date: 2007-05-01
Publication date: 2007-11-15
Anticipated expiration: 2027-05-01
Also published as: EP2019618A2; IL195047A0; EP2019618A4; WO2007130958A3; CA2650959A1; WO2007130958A2; AU2007248156B2

Description

WO 2007/130958 PCT/US2007/067906 PASSIVE PHONOGRAPHY HEART MONITOR BACKGROUND This invention relates to medical monitoring, and in r-particular fetal heart moni torm,1g. Fetal heart monitoring is a diagnostic tool to indicate the overall health status of a fetus. Currently deployed fetal heart monitoring techniques are primarily ultrasound, Doppler-baed. With a typical ultrasound Doppler-based technique, wires are deployed betwcen1 an ultra sound transducer uait and processing unit A skilled operator, such as a medical technician or nurse scans or places a transceiver on the abdomen of the patient. Typically, the operator covers a region on the abdomen with a gel and moves the ultrasonic ,sens.or around the area to scani the area. Alternativelv, the sensor can be. affixed with, a belt that is xworn around the woman., The belt is cuambersome and inaccurate (often the seansor slips off of its target) and it has to be removed prior to any surgery tor emerency procedure Acoustic siai are emitted from the transducers and their echo signals are detected by the transceiver arid processed to produce data pertaining to th-e feta heart rate. Current Doppler-based techniques for fetal monitorin,,g have several liitations. One limitation of current Dopplemrbased techniques is the lack of specificity for detecting fetal ear tones (FH.. In ca~es of maternal tachvcardia, the operator may not be able to diflerentiate Mw.ether the transducer is detecting t al or maternal signal, and this can have catastrophic consequenc. tdhe" limitations pertain to changes in fetal position or station which ofien, require re-positionimg o the transducer which can be time-consuming and result in "blackout" periods in fetal monitoring, ,tring which medical personnel do not receive data from imonitors that monitor the fes.' Aknother limitation is the loss of continuous monitoring in a distressed fetus, especially during transition periods. e. g., moving fro. a delivery room to an operating room for an energeinAcy Cesare, ian section, procedure. In addition, many hospital protocols require detachme.ntof all wires from fetal mnonito ing devices during room transfters. Detaching fetal moni tors begins another "I ackout penod. . Adrmi nistration of epidural anesthesia presents another potet l

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tbl ackout" period for fetal moni tring, a;s the transducer is frequently re-n oved or displaced d during that procedure. This. too. is a critical time frame for fetal monitoring, as epidural anesthesia rmay cause materna11 hypotension with sutbsequernt fetal bradycardia.

WO 2007/130958 PCT/US2007/067906 Maternal ambulation has been shown to facilitate labor progress, but current techniques typically preclude such standing deliveries. A newer monitoring technique k lown as fetial phonography uses a passive acoustic sensor to capture acoustic energy rnm the maternal abdomen. Typically. teo sensor includes a piezeectic element. In a paper entitled Deveennc ofa iezopolvmer Pstsre S'nsor for a Portabk/e Ftal Heart Rate Monitor" by Allan J. Zuckerwar et al, ,IEEE TRANSACTiONS ON BIOMEDICAL ENGINEERING VOL. 40, NO. 9. SEPTEMBER 1993 p. 963, the authors described a pressure sen-sor aray mounted onr a belt wotm by lthe mother. TIhe sensor array uses two polyvinyidene fluoride elements arranged in a bimorph structue, mechanical y in series and electrically in parallel SUMMARY According to an aspect of the present invention, a fltal heart monitor device includes a channel to receive a first signal representative of acoustic energy principally fr'om a maternal heartbeat and a second signal representative of acoustic energy including a fbtal heart beat The device includes a computing device including a processor, a memory operatively coupled to the processor and nonvolatile storage operativey coupled to the processor, the non-volatile storage storing a computer progpam includ instructions to cause the processor to process the first and second electrical signals into art electrical signal representing acoustic energy principally of the fetal heartbeat. The foiliwing are embodiments within the scope of the claims. The device includes a chanel to receive a third signal representative of acoustic energy of uterine contractions and the program includes instructions to process the third electrical signal into an indication of maternal uterine rates of contraction. The device includes instructions to process the second electrical signal to provide an electrical signal representative of acoustic energy principally of the maternal heartbeat. The device includes instructions to render the electrical signal representative of the fetal heartbeat on an output device. The device includes an audio speaker ard the electrical sign is rendered by the speaker to produce an audio representation of the fetal heartbeat. The device includes a display and the electrical signal is rendered by the display to produce representation of the fetal heartbeat. T"he device includes a display and the electrical signal is rendered by the display to provide a representation s of the fetal heartbeat rate. 2 WO 2007/130958 PCT/US2007/067906 The device includes a pair of acoustic transducers each comprising a polymer that exhibits piezoelectric properties, and which converts acoustic energy into the first and second signals. The device includes three acoustic transducers each comprising a olfnxer that exhibits piezoeiectric properties, md which converts acoustic energy into the first, second and third signals. The device includes a pair of acoustic transducers each comprising a polymer that exhibits piezoelectric properties, which converts acoustic energy into the first and second signals and a strain gauge that provides a third signal representative ofn materna contractions. The pair of transducers are coupled to the monitor, via wires or cables to provide the first and second sigmalns to the channel. Each of the first arind second transducers includes circuitry to wirel essly transmit data over the first and second channels to the monitor and the monitor inchides circu itry to receive the wirelessly transmitted data. The circuitry to wirelessly transmit data includes radio frequency transmitter circuitry. The circuitry to wire lessly transmit data includes circuitry to tranmsnit a unique transducer identification code to the m-onitor. Each transducer includes a polymer sheet ofpoly-,inyldene fluoride and/or co-polymers thereof According to a further aspect of the present invention, a method monitoring fetal heart beat includes receiving over a first channel, a first signal representative of acoustic energy principally from a maternal heartbeat, receiviOrng, over a second channel, a second signal representative of acoustic energy including a fetal heart beat and processing the first and second electrical signas into an electrical signal preresanting acoustic energy principally of the fetal heartbeat. The following are embodinments within the scope of the invention. The method includes converting acoustic energy representative of maternal uterine contractions into a third electrical signal. 'he method includes processing the first and second electrical signals to provide the electrical signal representative of acoustic energy principally due to the ftial heartbeat, the second signal to provide a signal representative of the maternal heart and the third signal to provide a sign representative of maternal uterine contractions. "'The method indudes rendering the electrical signals representative of the fetal heartbeat, maternal heartbeat and uterine contractions on an output device. The method includes applying principal component analysis digta representations of the signalIs The method includes wirelessly transmitting data from a pair of transducers disposed on the patient over the first and second channels to provide the first and second signals. 0 WO 2007/130958 PCT/US2007/067906 According to a fu:rth:e.r aspect of the present invention, a fetal heart monitor device includes a channel to receive a first signal representative of acoustic energy prhncipally fir-om a maternal heartbeat and a second signal representative of acoustic energy inchuding a fetal heart beat and circuitry to process the first and second electrical signals into an electrical signal representing acoustic energy principally of thle ftal heartbeat. The following are enibodirnents within the scope of the invention. The device includes a channel to receive a third signal representati-ve of acoustic energy of uterine contractions and circuitry to process the third electrical signal into an indication of maternal uterine rates of contraction. The device includes circuitry to render the electrical signal representative of the fdtal heartbeat on an output device. The devi ce in-cludes circuitry to modulate the fetal heart tone into the audible frequency Irange and an audio speaker to render an audio representation of the fetal heartbeat. The device includes a display to render a visual representation of the fetal heartbeat. The device includes a display to reader a value indicative of fetal heartbeat rate. One or more aspects of the invenCtion may provide one or more of the 1fo11owing advantages. The monitor is capable of fianctioning without a skilled technician being present. Additionally the monitor can be relatively low in cost compared to currently employed ultrasound based monitors by avoiding need for relativy expensive crystals commonly employed in the ultrasound transdtucers. The monitor uses low-cost sensing, transmission, and circuitry components suitable for operation in hospitals, physician ofifces, or home. IThe monitor uses transducer sensor units that are disposable. The disposal e nature of the transducer sensor tuaits enables the monitor to ensure a very high standard of accuracy for these transducer sensor units because the term of use for each transducer sensor unit will not exceed a specified time duration. Hence, normal concerns of quality degradat ion resultirg -from extended use are avoided, while maintaining a relatively high le vel of performance. The monitor avoids blackout periods, e.g., the potentially most dangerous window of time during labor since the monitor in the wired and. especially the wireless form allows for constant monito-ing. Accurate, wireless monioring system aids in decreasing labor time by increasing the potential mobility of the patient, thus making the resources in a labor-and-deli very unit more available. The monitor uses a pitch period detector, a principal component analyzer and a complex wavelet transform analysis techndique to analyze signals from the sensors. ThIis 4 WO 2007/130958 PCT/US2007/067906 permits sophisticated and accurate fetal signal processing to be employed in the monitor at a relatively low cost. The monitor allows for maternal ambuiation, during labor, providing a number of potential benefits. According to an additional aspect of the present invention, an acoustic transducer includes a base member, a polymer sheet having a pair of electrodes disposed over nnmajoT, opposing srtfaces of the olymer sheet, the polymer sheet disposed adjacent, an exterior portion of the base member a cap affixed to the base member and electrical circuitry carried by the acoustic transducer and coupled to the electrodes on the polymer sheet. The f.ilowing arec embodiments with the scope of the invention. The circuitry is disposed between the base and the cap. The cap has a convex surface. The cap and the base member are secured tog ether. The base has an aperture and the polymer sheet is supported in the aperture in the base by attaching a securing member to one of the major surfaces of the polymer, the one major sarface being on an external surface of the acoustic transducer. An exte or surface of the base member has an adhesive layer thereon to adhere the transducer to epidermis of a subject. The exterior surface of the base member has an adhesive layer thereon to support an outer one of the major surfaces of the polymer and .o adhere the transducer to epidermis of a subject. The adhesive layer provides an acoustic impedance coupling between the outer one of the major surfthces of the polymer and epidermis of the subject. The adhesive layer is a double-sided tape. 'The circuitry comprises a transmitting device to wirelessly transmit signals from the transducer. 'Aihe circuitry includes a low noise, high impedance amplifier coupled to receive a voltage potential produced across electrodes of the pol mer sheet and a transmitting device coupled to the output of the amplifier to wirelessly transmit an output signal from the transducer. The circuitry comprises circuitry to couple wires or cables to output signals fiom the transducer. The circuitry includes a low noise, high impedance amplifier coupled to receive a voltage potential produced across electrodes of the polymer sheet and a connector to couple signals from the amplifier to the wires or cables. The aperture in the base member is a generally rectangular aperture in a substantial portion of the base member. The aperture in the base member is a generally Y-shaped aperture having three regions, the aperture in a substantial portion of the base member and the acoustic transducer includes an additional pair of polymer sheets, with the polymer sheet and the addition pair of polymer sheets disposed in the three regions of the aperture, The base member and cover are secured together by a plurality ofsnap latches on one of the cover and base that mate WO 2007/130958 PCT/US2007/067906 with receptacles on the other one of the cover and base to secure the base to the cover. The transducer body is a round shape. The transducer is for heart, monitoring. The the polymer. sheets polyvinydene flu ride and/or a co-polymer thereof The base and cover are comprised of a relatively s'':rong plastic material that is sufficient in strength to support te weight of a pregnant woman. The the base and cover are comprised of an ABS plastic any of a class of plastics based on acryonitrile-butadcne-styrene copolyvers. The base has an aperture and the po vmer member is disposed within the aperture of the base. The base ha

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s an aperture i . ed with an acoustic foam materials and the polymer member is dis o ed within the aperture of the bas, The polyer member is disposed against the exterior portion, of Ie base, According to a f-rOther aspect of the present invention, an acoustic transducer includes a base member having an. aperture and a polymer sheet comprised of polyvinydene fluoride and./or a co-polyomer thereof, the sheet having a pair of electrodes disposed over major, opposing surfaces of the sheet, with the sheet disposed in the aperture in the base member. ,The transducer also includes a cap affixed to the base member and eectricat circuitry disposed in the acoustic transducer and electrically coupled to the electrodes on the sheet, The following are embodiments with in the scope of the invention. The circuitry includes a transmitter to transmit signals from the polymer sheet. The circuitry includes a low noise, high impedance amplifier coupled to receive a voltage potential produced across electrodes of the sheet and a transmitting device coupled to the -amplifier to wireless transmrnit an output signal from the amplifier. The cap has a co vex surface. The sheet s supported in the aperture by attaching an adhesive to one of the major surfaces ofthe polymer, the one major surface being on an external surfce of ithe acoustic transducer. The adhesive layer adheres the transducer to epidermis of a s'iject. The adhesive layer provides an acoustic impedance coupling between the outer one of the major surfaces of the polymer and epidermis of the subject. The adhesive layer is a double-sided tape. The circuitry includes ,.cuitry to couple wires or cables to output sigals fom he transducer. The eircu itrv includes a low noise, high impedance amplifier coupled to receive a Volt potential produced across electrodes of the sheet and a connector to couple signals from the amipli-fier to the wires or cables. The aperture in the base member is a generally rectangular aperture in a substantial portion of the base nmenber. The aperture in the base member is a generally Y-shaped aperture having three regions. the aperture irn a substantial portion of the 6 WO 2007/130958 PCT/US2007/067906 base member and wherein the acoustic transducer includes an additional pair of polymer sheets, witf thie polymer sheet and the addition pair of polymer sheets disposed in the three regions of the aperture. The transducer is for heart monitoring, The base and cover are comprised of a relatively strong plastic material that is sufficient in strength to support the weight of a pregnant woman. The base and cover are comprised of an ABS plastic any of a class of plastics based on acrylonitrile-butadietnestyrene copolTners, The base has an aperture filed with an acoustic foam materials and the sheet is disposed within the aperture of the base. One or more aspects of the invention may provide one or more of the bIllowing advantages. The transducers are affixed to the patient, which avoids the need fr a skilled technician to be present while a monitor attached to the transducers is operating. The transducers can be relatively low cost due to the use of the polyrner as compared to more expensive crystals used in Doppler techniques used with ultrasonic transducers. The transducers use low-cost sensing, transmission., and circuitry components suitable for operation in hospitals, physician offices, or home. The transducers are disposable. The disposable nature ofthe transducers enables the monitor to ensure a very high standard of accuracy for these trasducer sensor units because the term of use for each transducer sensor unit will not exceed a specified time duration. Hence, normal concerns ofquality degradation resulting from extended use are avoided, while maintaining a relatively high level of pertiormanrce. The wireless versions of the transducer when employed with a monitor can avoid blackout periods, e.g., the potentiallv most dangerous window of time during g labor since the wireless form allows for constant monitoring. Accurate, wireless monitoring system aids int decreasing labor time by increasing the poen tial mobility of the patient, thus making. the resources in a labor-and-delivervy unit more avalabie. According to a farther aspect of the present invention, a method includes converting acoustic energy representative principally of a maternal heartbeat into a first electrical signal, converting acoustic energy representative of a maternal heartbeat and a etal heartbeat into a second electrical signal and processing the first and second electrical to provide an electrical signal principally representative of the fetal heartbeat. The method further includes detemnnining pitch periods of the signal principally representative of the fetal heart beat.

WO 2007/130958 PCT/US2007/067906 The follow embodiments are within the scope of the invention. The method further includes converting acoustic energy representative of maternal uterine contractions into a third electrical signal. The method further incl udes rendering the electrical signal principally representative of the fetal heartbeat on an output device, The method further includes determining principal components of determined pitch periods of the signal principally representative of the fetal heartbeat. The method further includes modulating the electrical signal principally representative of the fetal heartbeat with a signal in the audible spectrum of human hearing, The mIethod further includes determining an initial period length value ofthe signal principals yv representative of the fetal heartbeat by finding a cepstru of the first fitw pitch periods of the signal principally representative of the fetal heartbeat to determine the requency of the signal. The method further includes determining a beginning and ending point of each pitch period in the signal principally representative of the fetat heartbeat. The method further includes determining a variation, of time durations between pitch, periods and using the lngth oft a prior period as an input to determine the duration of a subsequent pitch period. The further includes applying principal compoerit anrlalysis to the determined pitch periods to compress data representing the determined pitch periods. The method further includes processing the determined pitch periods to provide a representation, compressing the representation of the determined pitch periods, and storing the compressed representation of the determined pitch periods. According to a hrther aspect of the present invention, a computer program product residing on a computer readablie medium .tbr detecting feta heatbeat energy includes instructions to convert acoustic energy representative principally of a maternal heartbeat into a first electrical signal, convert acoustic energy representative of a maternal heartbeat and a fetal heartbeat into a second electrical signal, process the first and second electrical to provide an electric signal principally representative of the fetal heartbeat and determine pitch periods of the signal principally representative of the fetal heart beat The following are embodiments within the scope of the invention. The computer program product further includes instructions to convert acoustic energy representative of maternal uterine contractions into a third electrical sig nal. The computer program product further includes instructions to render the electrical signal principally representative of the fetal heartbeat on an output device. The computer program product further includes instructions to determine principal components of determined pitch 8 WO 2007/130958 PCT/US2007/067906 periods of the signal principally representative of the fetal heartbeat., The computer program product further includes instructions to modulate the electrical signal principally representative of the itali heartbeat with a signal in the audible spectrm of human hearing The computer program product further includes instructions to determine an initial period length value of the signal principally representative of the fetal heartbeat by finding a cepstrnm of the first few pitch periods of the signal principally representative of the fetal heartbeat to determine the frequency of the signal The computer program product further includes instructions to determine a beginning and ending point of each pitch period in the signal principally representative of the fetal heartbeat. The computer program product father includes instructions to determine a variation of time durations between pitch periods and use the length of a prior period as an input to determine the duration of a subsequent pitch period. The computer program product further includes instructions to apply principal corn ponent analysis to the determined pitch periods to compress data representing the determined pitch periods. The computer program product further includes instructions to process the deten-rmined pitch periods to provide a representation., compress the representation of the determined pitch periods and store the compressed representation of the determined pitch periods. According to an additional aspect of the present invention, an apparatus includes circuitry to convert acoustic energy representative principally of a .raternal heartbeat into a first electrical signal, circuitry to convert acoustic energy representative of a maternal heartbeat and a fetal heartbeat into a second electrical signal, circuitry to process the first antd second electrical to provide an electrical signal principaly representative of the fetal heartbeat and circuitry to determine pitch periods of the signal principally representative of the fetal heart beat. The following are embodiments within the scope ofthe invention. The apparatus inmciudes circuitry to convert acoustic energy representative e of maternal uterine contractions into a third electrical signal. The apparatus i'cldees 'ircuitry to render the electrical signal principally representative of the fital heartbeat on an output device. The apparatus includes circuitry to determine principal components of determined pitch periods of the sigrnal principally representative of the fetal heartbeat. The apparatus includes circuitry to modulate the electrical signal principally representative of tfhe fetal neartheat with a signal in the audible spectrum of human hearing. The apparatus includes circuitry to determine an initial period length value of the signal principally representative WO 2007/130958 PCT/US2007/067906 of the fetal hl-eartneat by finding a cepstrium of the first few pitch periods of the signal prin..cipally representative of the fetal heartbeat to determine the fIequency of the signaL The apparatus includes circuitry to det rmin i e a begging and ending point of each pitch period in the signal principally representative 01oFtihe f tal heartbeat, The apparatus includes circuitry to determine a variation of time durations between pitch periods and circuitry to use the length of a prior period as an input to detennine the duration of a subsequent pitch. period. The apparatus includes circuitry to apply principal components analysis to the de.-temnnined pitch periods to compress data representing the determined pitch periods. The apparttus includes Circuitrv to process the determined pitch pe riods to provide a repreetation, compress the representation of the determined pitch periods and store the compressed representation of the determined pitch periods. One or more aspects of the invention may provide one or more of the allowing advanta ges, The monitor is capable of functioning without a skilled techician being present Additioarally the monitor can be relatively low in cost compared to currently emrplo yed ultrasound based monitors by avoiding need fbr relatively expensive crystals commonly employed in the ultrasound transducers. The monitor uses low-cost sensing, transmission. and circuit ry components suitable obr operation in hospitals, physician offices, or home Ovionniants, The monitor uses transducer sensor units that are disposable. The disposable nature o - the transducer sensor units enables the monitor to ensure a very high standard of accuracy for these transducer sensor units because the term of ise for each transducer sensor u-nit will not exceed a specified time duration. Hence, normal concerns of qua ity degradation resulting from extended use are avoided, whie maintaining a relatively high level of performance. The moiutor avoids blackout periods, eog. the potentially most dangerous window of time during labor since the monitor in the wired and especially the wireless fbrm allows for constant monitoring. Accurate, wireless monitoring system aid in decreasing labor time by increasing flthe potential mobility of the patient, thus making the resources in a iabor-and-deliverv unit more available. Ti1e monitor uses a pitch period detector, a principal component analyzer, arnd a complex .wavelet iter bank to .analze signals from the sensors. This permits sophistJcated and accurate fetal signal processing to be employed in the monitor at a relatively low cost. 10 WO 2007/130958 PCT/US2007/067906 The monitor allows tor maternal anibalation during labor, providing a number of potential benefits. Acco rdi'ng to an aspect of the present invention, a method of acoustic monitoring includes tranisducing acoustic energy from a first acoustic transducer attached to a first location on a patient the acoustic energy from the first transducer, comprising desired acoustic energy to be monitored and interfering acoustic energy, transducing acoustic energy from a second acoustic transducer, attached to a second, different location on a patient, the acoustic energy from the second tranmsducer, comprising desired acoustic energy o be monitored and interfering acoustic energy, converting the acoustic energy sensed at the first and second locations into first and second electrical signals and processing the first and second electrical signals to digi.tally remove intertering acoustic energy pre sent in the second signal to provide an electrical signal representative ofthe acoustic signal that is being mornitored. The flowing are embodiments within the scope of the invention. The interfering acoustic energy is principally representative e of a maternal heartbeat. The acoustic energy to be mon stored includes acoustic energyrepresertative of a fetal heartbeat and processing the first and second electrical signals provides the electrical signal representative of the fetal heartbeat. The method includes transducing a plurality of signals from a phIrality of transducers, including the first transducer, the plurality of signals representing the acoustic energy to be monitored and processing the first the plurality of signals along with the second electrical signal to provide the electrical signal representative of the acoustic energy to be monitored x, The acoustic ene y to be monitored includes acostic energy representative of a fetal heartbeat and processing the plurality of signals including the first signal, and second electrical signals provides the electrical signal representative of the fttal heartbeat. According to an aspect of the present invention, a method of monitoring health status of a fes includes transducing acoustic energy rom a first acoustic transducer attached to the epidenrmis about the vicinity of the abdomen of a pregnant woman, the acoustic energy from the first transducer, comprising acoustic energy of a fetal hearbeat and interfering acoustic energy of a maternal heartbeat, transducing acoustic energy from a second acoustic transducer, attached to the percordium region of a pregnant woman., the acoustic energy, from the first transducer the acoustic energy from the second transducer comprising the interfering acoustic energy of the maternal heartbeat, converting the acoustic WO 2007/130958 PCT/US2007/067906 energy sensed at the first and secod locations into Nirst and second ectical signals and processing the first and second electrical signals to provide an output sTgnal representative of the tal hearl.beat. The interfering acoustic energy is removed during processing of the first and second signals. The process includes processing at least tUe second elecAtrical signal to provide a second output signal representative of the maternal heartbeat. The second transducer is attached beneath the percordium area of the patient. The method includes converting acoustic energy representative of maternal uterine contractiPons into a third electrical signal The minetnod includes processing the third electrical signal to provide a signal representative of a rate of mnaternal uterine contractions. The method is applied to monitor fetal heartbeats and includes attaching the first transducer to the abdominal region of the patient in a region where the back cf the fetus is against the maternal abdominal wall. The method includes rendering the electrical signal representative of the fetal heartbeat on an output device. The output device is an audio speaker. 'The output device is a display device that renders an electrocardiogram. The output device is a display device that renders readout of heartbeat rate. The method includes rendering the second output signal representative of the maternal heartbeat on an output device. The acoustic transducers are wireless. The acoustic transducers are coupled to a processing device via cables and/or wires. One or more aspects of the invention may provide o.ne or more of the following advantages. The monitor is capable of functioning without a skilled technicianm being present. Additionally, the monitor can be relatively low in cost compared to currently employed ultrasound based monitors by avoiding need for relatively expensive crystals comnmnonly employed in the ultrasound transducers. The minonitor uses low-cost sensing, transmission, and circuitry components sitable for operation in hospitals, physician offices, or home. The monitor uses transducer sensor units that are disposable. The disposable nature of the tranasducer sensor units enables the monitor to ensure a very high standard of accuracy for these transducer sen sor units because the term ofu se for each. transducer sensor unit will not exceed a specified time duration. Hence. normal concerns of quality degradation resulting from extended use are avoided, while maintaining a relatively high level of perfonmnance. The monitor avoids blackout periods, e.g,, ithe potentially most dangerous window of time during labor since the monitor in the wired and especially the wireless fi.rm 12 WO 2007/130958 PCT/US2007/067906 allows for constant monitoring., Accurate, wireless monitoring system aids In decreasing labor time by increasing the potential mobility of the patient, thius making the resources in a labor and-deiivery unit more available. The monitor uses a pitch period detector and a principa component analyzer to analyze signals from the sensors. This permits sophisticated and accurate ital signal processing to be employed in the monitor at a relatively low cost. The monitor allows for maternal ambulation during labor providing a number of potential benefits. The details of one or more embodiments of the invention are set forth, in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. DESCRIPTION OF DRAWINGS FIG. 1 is a block diagram of a monitoring scheme. FIG, 2 is a block diagram of fetal monitor device used to mon itor fetal cardiac activity. FIG 3 is a flow chart depicting aspects of processing in the fetal monitoring device of FIG 2. FIG 4 is a block diagram of an alternative fetal monitor device. FIG 5 is a block diagram depicting processing. FIGS. 6A-6F- A-C (collectively FIGS. 6-8) are diagrams depicting construction details of sensors used with the monitor of FIG 3. FIGS. 9A-9B (collectively FIG 9) is a set of diagrams depicting an alternmate pattern for a piezoelectric sensor element. FIG 10 is a block diagran of circuitry used in the sensors. FIG I I is a schematic of a high impedance amplifier used with the sensors of PIGS. 6-8. FIG 12 is a block diagram depicting details of pitch processing FIG 13 is a flow chart depicting pitch processing, FIGS. 14A and 14B13 are diagrams useful in understanding processing of fetal and matenal heartbeat sigals. FIt 15 is a flow chart depicting principal components analysis 13 WO 2007/130958 PCT/US2007/067906 DETAILED DESCRIPTION Referring to FIG. 1, an arragement 10 for connect , of a monitor device 12 ("monitor") ,to a patient, e.g, pregnat woman 4 to monitor fetal heartbeat signals is shown. The monitor 12 can be used for various types of monitoring, as discussed below, hi. this example, thle moni tor 12 is a fetal heartbeat m.noi tor. The monitor 12 (discussed in detail below) has acmoustic transducer (sensors) 16a- 16 that convert acoustic energy from the pregnant woman 14 into electric energy. The tran ducers 16a- 16c are coupled to the monitor 12, via communications channels, 18a

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k I Sc, which can be wires connecting to the monitor 12 or wireless channels (radio frequency, optical andior infiared). In one embodiment, Bluetooth-® wireless technology is used. i one configuration for connection of the monitor 12 to the patient, one of the transducers, e.g trm sducer 16a monitors the pregnanta woman's heartbeat, another one of the transducers b monitors the pregnant woman's uterus to measure uterine contractions The transducer to monitor the uterine contractions, is not essential to capturing the fetal heartbeat but is included as part of an overall tool to monitor the health and status of the patient and fetus. The third transducer I6c monitors the fetal heartbeat. The ocation of tfhe opCregnant woman' heart anmd uterus are readily predictable. The acoustic energy fromn the fetal heart is omni-directional but localized about the back of the fetus. Such localization is attributed to preferred acoustic propagation to sites where the fetal back is against the maternal, abdominal wall. The acoustic propagation through the nuema-l wali , omi directional but there is a point of maximum acoustic conduction, which is the point where the fetus' back is pressed against the uterine wall. However, other positions can be used to attach the transducer 16c to the pregnant woman. in another confi duration for connection of the mrnonitor 12 to the patient., transducer 16a is arranged to monitor the pregnant woman's heartbeat ad transducers .6b monitors the pregnant woman's uterus to measure uterine contractions. To capture fetal acoustic energy, a plurality of transducers (not shown) 16c canbe deployed tom onitor the fetal heartbeat. The multiple acoustic transducer 16c are deployed fbr fetai detection ,and arranged about the maximal fetal acoustic energy. This is a noise reduction technique that can be used in cases where it is difficult to sense the fetal heartbeat (e.g in the case or an overweig.t pregnant woman or underweight fetus) extra fetal sensors can he de-oyed to boost the strength of the fetal signal. Furthermore, 3 or more fetal sensors can be used to 14 WO 2007/130958 PCT/US2007/067906 triangulate the position of the fetal heart. This localization information can he used by doctors and technicians during labor and delivery. Re.ferring to FIG. 2, the monitor 12 includes a processor 30, e.g., a general purpose central processing unit (CPU) and/or a digital signal processor (DSP) to process signals from the patient, a memory 32, to execute programs, persistent, e.g. non-volatile storage 34, and 0 interface(s) 36 all coupled via a bus 38. Executed by the monitor 12 is signal processing software 50 that processes ECCG signals detected by trantsducers 14a and 1 4c from -the pregnant womas heart and the fetus's heart, respectively. The monitor 12 also processes signals from the transducer 14b that monitors fobr contractions in the pregnant womn-S uterus. Processing 50 provides a relatively clean detection of the fetal heartbeat by elimniating major sources of noise in the fetal heartbeat signal, e.g., the relatively strong acoustic energy components contributed to the detected fetal heartbeat caused by the pregnant woman's heartbeat. In some embodiments, acoustic energy components from uterine contractions could also be filtered from the detected fetal heartbeat acoustic energy, but in general that is an insignificant contributor to noise in detection of the fetal heartbeat. The monitor I 0 can also include other user interface devi ces, e.g., keyboard or keypad. a display, speakers, headphone, etc. (not shownn. in addition, the monitor can include a. transmission channel to upload data to a server or the like. Referring to FIG. 3, the monitor 12 includes an interface 36 that interfaces the monitor 12 to the transducers I 6a-16c. The interface 36 here is shown to include chamncls 36a-36c fibr transducers l6a-16c, respectively. Each channel 36a-36c includes a receiver 40 (if th-e monitor is a wireless version) or an analog signal interface (not shown) to cables (not shown) from the transducer, if the monitor 12 is a wire-connected version. In addition, the interlIee 36 includes a low noise amlifier ad a filter generally42 to process analog signals from the transducers - 1ai6c. The ampiifier 14 amplifies the signals and the filter filters the signals to preserve frequencies in. the range of, e.g., 0.05 to 100 l-lz or so. Typically, the fetal channel in the monitor 12 can be within the broad range above, but most likely will in, a range about 0 to 30 i-z and especially in a range of 18 to 25 Hz (the range ofnmaximtal spectral power ofthe fetal heart signal). The maternal channel can be within the broad range above. but most likely will in a range about 6 to 14 Hz and especially in a range of 8 to 12 Hz (the region of maximal power of the maternal heart signal), Whereas, the transducer 14b that senses the 15 WO 2007/130958 PCT/US2007/067906 maternal contractions need not have any filtering since itis a very long period, e.g., a large inpul'se Each amplifier 14 feeds the signal to an A/D converter 44 that digitizes the signal, at a sampling frequency at least greater than twice the highest frequency cmponent in the channel. In other implemnentations, a single A/D converter and a nultiplexer can be used to process data from the channels (See FIG. 4). The digitized signals from each of the channels are transferred to the bus interface device 46 that formats the digit zed signals to place on the bus 38 (FIG.1 2) to send to the memory 34 and/or processor 32. i be processed, R.efrring to FIG. 4, an alternative arrangement for the monitor 1 2 iriterfaces the monitor 12 to the transducers I 6a-16c. A channel 36ai36c is provided for each transducer i6a-1 6c. Ekach channel 36a-36c includes a receiver 40 (if the monitor is a wireless version) or an analog signal interthce (not shown) to cables (not shown) from the transducer, if the monitor is a wire-comnnected version. In addition, the interfaces 36a to 36t include a low noise amplifier and a filter generahy 42 to process aalog sigjls from the transduocers 16a and 16c and a low noise amplifier generally 42' to process analog signaIs from the transducer 106b. The amplifier 14 amplifies the signals and the filter filters the signals to preserve frequencies in the ranges discussed above. Each amplifier/filter 42 anad amplifier 42 selectively feeds its output signal to a A/D converter/'multiplexer 44 that digitizes the signal., at a sampling frkequency at least greater than twice the highest frequency components in the channel, according to control provided from the processor. The single AID converter and na.ltiplexer 44 processes data in the selected channel and transfers the data to the digital signal processor 45 (DSP) for processing described below. A processor 48 processes signals from a front panel to control the ADC/Oux 44, whereas the DSP 45 processes output signals from the ADCimux 44 to provide outputs to the front panel, Ir some implementations this can be the same device. The front panel thus includes a display, a digital readout, switches (to select which channel to process), speakers, and so f brth. The monitor 10 can also include other user interface devices, e.g. keyboard or keypad, and interfaces for connection to other equipment to upload data to a server and the like. The arrangement also includes memov to execute programs, persistent, e.g., non volatile storage, and i/O interface(s) all coupled via buses (not shown) to the digital signal processor 45 and processor 48. 16 WO 2007/130958 PCT/US2007/067906 Executed by DSP 45 is signal processing software 50 that processes signals from the transducers 16a and 16o from the pregnant woman's heart and the fetus's heart, respectively. The monitor also processes signals from the transducer 16b that monitors for contractions in the pregnant woman's uterus. T[his data are td to the processor to determine contraction rates that are sent to the front panel tfbr display. Processing 50 provides a relatively clean detection of the fetal heart eat by eliminating mrajior sources of noise in the fetal heartbeat signal, e.g,, the relatively strong acoustic energy componne.nts contributed to the detected fetal hearthbeat caused by the pregnant woman 's heartbeat. In some embodiments, acousic energy components from uterine contraction's could also be filtered from the detected fetal heartbeat acoustic energy. R evening to FIG 5 , processing of signals from the trmansducers is shown. The signals from channels 36a, 36c are passed through digital band pass filters 51a 5Ib to filter the signals in the range discussed above, e.g., 18 to 25 Hz bfor the fta channel and 8 to 12 Hz for the material channel, The other ranges above could be used. The component of the pregnant woman's heartbeat that appears in the fetal channel is removed from the fital signal in the difference block 5 Ic. From the difference block, the signal is fed to a pitch track processor 52. The pitch track processor 52 uses pitch tracking and a principal component analysis to generate waveforms that can be used to determine heart rates, e.g., in heart rate processor 55 and process the signal to provide an ECG from EG processor 56. These signals can be displayed on display 58. The modulator 54 takes the output signal firomn the difference block 51 d and modulates it with a signal in the audible spectrum of human hearing. That is the modulator adds a earnrier to the signal from the difference block 51 d to provide an outptt signal that can be heard by humans. This signal can be converted to an analog representation and fLd to an audio amplifier, to be rendered from a speaker 5Rb, etc. Details of processing are discutissed below. Retferring to FIGS. 6A-6E through 8A-C, collectively FIGS. 6-8, details of construction fbr an acoustic transducer "button" 16c trawisducer to acquire sound waves in the audible spectrum from the fetal heart are shown. A similar arrangement can, be used for the transducer 16a to acquire the maternal heart beat signal and transducer 16b, the tocodvnamometer (TOCO) transducer to detect maternal contractions, as further described below. 17 WO 2007/130958 PCT/US2007/067906 Transducer 16c is a relatively smdl, self-adherming, device that, in some implementations, is wireless. Transducer 16c is attached to the epidermis of the maternal abdomen, via a layer of an adhesive, e.g., an adhesive tape 61, in particular a double-sided adhesive, which in addition to providing for attachment of the tranisducer 16ce to the epidermis also provides acoustic impedance matching between the epidenn-is and a piezolectric mlcntbrae that detects acoustic energy in the transducer. The transducer 16c captures acoustic energy that emanates from the maternal abdomen through the uterus. Refrring to FIGS. 6A-6E, collectively, FIG. 6, the acoustic transducer "button" 16c includes a base member 60. The base member 60, as depicted in FIG., 6A, includes a frame arrangement 62 that supports bosses 64 to carry a circuit board (not shown) that supports signal preconditioning circuits, as discussed in FIG. 9. FKI. 6A depicts an aperture 66 in a bottom portion 60a of the base 60. A polymer membrane 68 covers a substantial portion of the aperture 66a. The polymner membrane 68 is sandwiched between a pair of electrodes over the opposing m major surfthees of the polymer membrane 68. A pair of wires (not shown), br example, are attached to flie electrodes of the polymer 68. Bosses are provided in the base 60 to elevate a circuit board above the plane of the bottom of the base 60 to provide clearance for wires, that couple to the electrodes on the polymer membrane 68. As shown in FIG. 6B13, the polymer membrane 68 is disposed through a cavity 65 in the bottom of the base 60, such that the polymer membrane 68 rests within but is not interfered with by sides of the base 60 that form cavity 65. The cavity can be eliminated. For instance, depending on. manufacturing constraints other configurations such as cornnectIng the PCB to the membrane via electrodes provided through the base mnay be preferred. in addition a lbam type material can occupy the cavity, e.g , the cavity can, be filled with another material, e.g., an acoustic fbam material. The polymer membrane 68 has a major surface that is contacted by the double-sided adhesive tape 61 on what will be the outside of the base 60, as shown in FIG. 6C, and a secon-d malor surf ce that is within the transducer, TIhe adhesive layer 61 is provided on the bottom of the base an.d over the outside surface of the polymer menibrane 68. In general, the adhesive lawyer contacts the polymer iemibrane 68 on. the outside, major surface, thus securing the polymer membrane 68 into the transducer. T he adhesive 69 is provided as a double-sided adhesive medical-grade tape of a 4.5 mil double coated polyester tape, coated on both sides with a hy- oalergenic, 18 WO 2007/130958 PCT/US2007/067906 pressure sPsitive synthetic rnbber based adhesive on a Iil trasparet peter caer with a release liner silicone coated 60 lb bleached Kraft paper. This tape is et.hyiene oxide, ganmmuna and autoclave process tolerant. One suitable product is Tape No. 9877 -m 3M Corporation Minneapolis MN. Other adhesive tapes and adhesives could be used. in conventional approaches, as mentioned above an acoustic match is provided by a gel that is applied on the maternal abdomen. Typically, .the operator covers a region of the abdomen with the gel (a slippery, non-sticky clear gel) and moves the uatrasonic sensor around the area to scan the area. Alternatively, the conventional umtrasonic sensor can be affixed with a belt that is worn around the woman. 'The belt is cunibersome and especially accurate (since often the sensor slips off of its target) and it has to be removed prior to surgery or emergency procedures. In contrast, the adhesive tape 61 secures the polymer membrane to the transducer 16a, hoidimg one major surface of the polymer, e.g., the outer surface of the polymer, while permitting the other major surface of the polymer 68 to be free to vibrate in the cavity 65 of the transducer, The adhesive tape 61, as discussed above, provides acoustic coupling between the polymer 68 and the matemal abdomen. ha some embodiments, material can be interposed between the tape and the polymer mnembrane for additional acoustic imnpedance matching. Bere the tape 69 provides acoustic impedance matching, while securing the polymer 68 to the transducer 16c and also securing the transducer 16c to the abdomen of the patient. As depicted in. FIG 6D, a snap member 71 is disposed on an inner portion. of the sidewall of the base member 60, to fiasten a dome cap member 74 (FIGS. 7A-7D)) to the base member 60. Here five additional snap members are disposed about the base, adjacent to the bosses, as denoted by "S." FIG. 6E shows a side view of the base member 60 f'rom a side opposing the slot 69. Referring to FIGS. 7A-7D, collectively FIG. 7, the dome cap member 80 is illustrated The dome cap 80 has a generally convex outer surfahee, as depicted Ri FIG. 7A. The dome cap member supports a set of binding posts 82 that align with the base member 80 (FIG, 6) to secure the circuit board (not shown) inside the dome cap 80) and urge the circuit board against the bosses 64 on the base member 60, as depicted in FIG. 7C. The dome cap 80 has a generally convex outer surtice to increase the mechanical integrity of the tranisd aer housing. 19 WO 2007/130958 PCT/US2007/067906 FIGS. 7C and 7D depict details of the snap receptacle member 84 to secure the dome 80 to the base 60. Other fastening arrangements are possible ineuding gluing, screw thste ing welding and so ford. The base 60 and the dome 80 are comprised of a generally translucent material. One type of material for the dome 80 and base 60 is ABS, especially medically approved ABS. ABS is a plastic, especially any of a class of plastics based on acrylonitriie4bmadiene styren.e copolmers. ABS has sufficient strengthli to support the weight ofa pregnant women should she roll over onto the transducer, is medically approved, and is translucent. Other types ofrn materials, especially plastics having sufficient strength and prelferably translucence or transparency could be used. By using a translucent (or transparent) plastic, an optical type of indicator, such as a light emitting diode (LED) can be coupled to the circuitry inside the device. One or a series of LED's can be used to indicate status and health of the transducer, as discussed below. The LED's could also be outside of or moun'ted into the base or dome the device. Referring to FIGS. 8A-8C, the assembled transducer 16ce is illustrated with the base member 60 secured i n place to the dome cap 80, with the polymer membrane 68 exposed on the bottom with the adjacent cavity 66. Referring to IGS 9A-)B, collectively FIG. 9, an alternative construction is shown. Here the base member 60' has a aperture 66' that is in a generally "Y" shape, e. g., with three rectangular aperture regions converging together, in which are disposed three (3) polyrner membranes 68a-68c. The membranes 68a-68c improve sensitivity and can tbe electrically coupled in series to increase the overall voltage produced ftom the patient or in parallel to increase the amount of charge and hence reduce the input impedance for the high impedance amifiter. The polymer membrane 68 or 68a-68c can be comprised of a.,ny suitable polymer material that exhibits piezoelectric properties. Certain polymer and copolymer materials such as polyvinvyidene fluoride (PVDF) have long repeating chains of "CH CII" molecules that when "orientated" provide a crystalline structure and a net polarization. Such a sheet of orientated material disposed between a pair of delectrodes, for example, can detect mechanical energy by producing a net charge or produce mechanica energy by application of charge, Films can be obtained from Measurement Specialties Inc. Valley Forge PA as part No. SDT'. -028k. which is equivalent to DTI-028k whose properties are in the table below, 20 WO 2007/130958 PCT/US2007/067906 but without a protective urethane coating. This is a 028 micron thick poyinmer sheet with Silver ink electrodes although NiCa-alloys could be used. Leads can be placed oni separately or can be provided by the manufacturer. Leads can be attached by compressive clamping cis,eyevlets, conductive epoxy or low temperature solders and so forth. Number A B C D E in electrode film cetrode tIhickess p,-, C-t"'t T 028K ,34 ( 6) .484 ( 12)' 163 (41) 1.19 (30) 40" 138 4 Where dimensions A-E are in millimeters (mrn), F is capacitance (ni) nanofa-rads and where A and C are the width and length of the filUm, B and D are the width and length of the elect-rode and F is the thickness of the PVDP polymer. Other thicknress, sizes and types )f piezoelctric PVDF polymer could be used, In on e mode of operation, mechanical energy in the tr of acoustic energy from the pregnant woman (detected fetal and maternal heartbeats or detected contractions) impinge upon the combination of electrodes and sheet of material causing mechanical defiorming of the orientated crystalline structure of the sheet T'his mechanical deformation produces a voltage potential across the sheet of material, providing a potential difference between the pair of ectrodes. This potential difference is amplified by the circuitry on the circuit board, is preprocessed, and transmitted to the monitor 12. The transducer 16a for in measurement of audible spectrum sound waves from the maternal heart caI be constructed in a similar manner. This button will be a tachei to the epidemlis,' e.g. the precordium, and will sense acoustic waves and send the signal to the interface 36 tbfor processing. In general, the precordium is the external surface of the body overlying the heart and stomach, typically, in the case of a pregnant woman, under the let breast of the patient, A tocodynarnometer (TOCO) transducer 16b for measurement of m atemnal uterine contractions is also constructed in a similar manner. The tocodynamnomeniter (TOCO) transducr 16b like the other transducers is a self-powered device, at least ,in wireless applications. The tocodynamometer (TOCO) transducer 16b is a small, self adhering device that detects contractions of the muscles of the pregnant woman', s uterus by sensing tightening of the maternal epidermis in the vicinity of the ut,,ers . ducer 16b i sim lar in con struction to the transducers 16a and 16c,. and is coupled to the monitor, via one of tihe WO 2007/130958 PCT/US2007/067906 input channels. Tlhe signal from the transducer 16b is processed to provide a measure of the rate of contractions of the uterus. n an alternative embodiment, the TOCO transducer 16 is a conventional strain gauge, which does not require the acoustic equipment of the heart beat monitor. Together, transducers 16a and 160 comprise a, transducer system. fbor capturinl acoustic energy that can include the fetal heart signal and with the analysis described in FIGS. 4 and 5 can produce an audible and acoustic signal, of the fetal heart from which the fetal condition can be ascertained. In addition, the transducer 16a and 16b provide a transducer system that provides signals that when processed provide an indication of the labor status of the pregnant woman, e.g., heart rate and rate of uterine contractions, The set of transducers 16a-I 6c provides minimal discomfort to the pregnant women , complete transparency with regard to the currently employed delivery room fetal monitoring techniques, and minimal and virtually no interference with emergency surgical procedures such as emergency cesarean section., especially with the wireless embodiments The wireless communication employed is low-power radio-ffequincy (RF) signals in compliance with FCC regulations posing no risk (according to contemporary medicoe views) to the pregnant woman, the infant, or any technicians and clinicians. One preferred. wireless technology employed is low power, Bluetooth'! (Biuetooth,@ SICG, Ine.) wireless teclrnclogy approved for medical applications. Referring to IG. 10, circuitry 1 00 on the circuit board housed in the transdkicer 160 is shown. Thle circuitry 100 inclu des a high impedance ampliiler 102 that interfaces to wires from the electrodes on the polymer membrane 68, as well as a battery 104 and a transmitter device 106 (or a analogy driver circuit (not shown' i tI-he transducer I e is coupled to the monitor 1 2 via wires. Also included is an antenna el ement 108, here a dilxlie antenna internal to the transducer, An on-chip antenna device may also be used Other techniques could be used such as infrared or optical. In a wired implementation, power to the devices could be delivered via wires that attached to the transducer, whereas in the wireless implementation power is provided by a smail battery, as shown in FIG. 101. In one wireless implementation each transducer includes a unique device identifier code 105. In operation, each transducer 16a-16c when powered up would first be registered with the monitor 12, eg., a procedure that stores in the monitor 12 the unique identifier of 22 WO 2007/130958 PCT/US2007/067906 the transducer that the monitor is wireless coupled to, Each time the transducer sends data to the monitor, the tranisducer includes the transducer identifier, so that the monitor would be certain that it is processing data fraomn the correct transducer, registered fbr that nmonito and nrot tom transducers registered with a different monitor and on a different patient, The circuitry also includes LEDS, here three being shown that li ght up to indicate various statuses of the transducer. For instance, using the situation of wireess transducers, the three LEDS., one red, one yellow and one green, can be used to indicate the statuses of respectively, 'Vdure", e.g., ofa battery, as shown or by failing to receive any output signal from the transmitter; '"ready but not registered" by sensing a signal from the transmitter, which would be in that case a transceiver, 'hich would receive a signal back from the monitor indicating that it is registered with the monitor; and "working" by sensing the output the transmitter. Alternatively, the LEDs can sense outputs fiom the amplifier. Referrning to PFIG i, I the high impedance mnplifier 102 is used to interface with the polymer sheet 68, Since the polymer sheet 68 is capacitive in nature, a high input inpedance amplifier is used to amplif, the voltage potential generated across the polymer sheet prior to transmission (either wirelessly or with wires) to the motor The high impedance amn-plifier 102 has components to set the operating point of the high impedance amplifier 102. The high impedance amplifier 102 includes an operational anmplifier 104 having differentiali inputs one of which receives a portion of the output signal fed back to the inverting input -INA of the amplifier 104. The signal fbiom the sheet 68 is fed to the non-inverting input +iNA. Referring now to FIG. 12, details of the pitch processing block 52 are shown. From the difference block, 5 d (FIG. 5) the signal is fed to pitch track analyzer 120, a switch 122, a principal component analysis (PCA) generator 124 and a spacing coefficient generator 126. Principal component analysis (PCA) is a linear algebraic transform, PCA is used to determine the most efficient orthogonal basis lbr a given set of data. When detennining the most efficient axes, or principal components of a set of data using PCA. a strength (ie., an importance value called herein as a coefficient) is assigned to each principal component of the data set, The pitch track analyzer 120 determnines the pitch perinods of the input waveobrma. The sigmd switch 122 routes the signal to the PCA generator 124 during an initial calibration period PCA generator 124 calculates the principal components for the initial 23 WO 2007/130958 PCT/US2007/067906 pitch period received. PCA Generator 124 sends the first, e,.g..6 principal components fr storage 130 and/or further processing. After the initial period, switch 122 routes, the signaril from the difference block to coefficient generator 126, which generates coefficients Ror act subsequent pitch period. instead of sending the principal components, oly the coetfficints are sent, thus reducing the number of bits. Swtch. 16 inchides a mechanism that determines if the coefficients being used are valid. Coeicients deviating from the original coefficients by more than a predetermined value are rec eted and new principal components and hence new coefficients are determined. 'e pitch tracking analzer 120 and the other components mention above are described in US. Patent Application Serial No. 10/624,139 filed July 21, 2 0 03, published

US-

20 0 4-01 02965-Al May 27, '2004 by Ezra J, Rapoport incorporated herein by reference in its entirety. The pitch track a.ialyzer 120 determines the pitch periods of the input waveorn. The pitch track analyzer 120 determines trends in the slight changes that modify a waveform across its pitch periods including quasi-p r±dic waveforms like heartbeat signals. in order to analyze the changes that occur from one pitch period to the next, a wavelrbmn is divided into i.ts pitch periods using pitch tracking process 3 (FI(G 13). Referring now also to FIG 13 a pitch tracking process 121 receives 121 a an input waveform 75 (FI G. 14A) from difference block 51 c to determine the pitch periods. Even though the waveforms of fetal heartbeat are quasi-periodic, a fetal heartbeat still has a pattern that repeats for the duration of the input waveform 75. However, each iteration of the pattern, or "pitch period" (e.g., PP) varies slightly from its adjacent pitch periods, e.g.,

PP

0 and PP,. Thus, the waveforms of the pitch periods are similar, but not identical. thus Mnalkng the time duration fr each pitch period unique. Since the pitch periods in a waveform vary in time duration, the number of sanmplirg points in each pitch period generallv differs and thus the number of dimensions required for each vectorized pitch period also differs. To adjust for this inconsistency pitch tracking analyzer 120 designates 121 b a standard vector (time) length Vj, After pitch tracking process 12.1 executes, the pitch tracking analyzer 120 chooses the vetor length tobe the average pitch period length plus a constant, e.g., 40 sampirng points. T''his allows for an average buffer of 20 sampling points on either side of a vector. The result is that all vectors are a uniforl n, length and caa be considered members of the same vector space. s, 241 WO 2007/130958 PCT/US2007/067906 vectors are returned where each vector has the same length and each vector includes a pitch period. Pitch trackiing process 121 al] so designates 121 c a buffer (time) length., B, which serves as an offset and allows the vectors of those pitch periods that are shorter than the vector length to run over and include sampling points from the next pitch period As a result, each vector returned has a buffer region of extra information at the end. This larger sample window allows for more accurate principal component calculations (discussed below). In the interest of storage reduction, the but'r length may be kept to between 10 and 20 sampling points (vector elemcnents) beyond dtec length of the longest pitch period in the waveform. At 8 kHz, a vector length that includes 120 samniple points and an offlset that includes 20 sampling units can provide optimumi results. Pitch tracking process 121 relies on the knowledge of the prior period duration, and does not determine the duration of the first period in a sample directly. Therefbre, pitch tracking process 1 21. determines 121 d an initial period length value by finding a real "Cepstrum" of the first few pitch periods of the heartbeat signal to determine the frequency ofte sigrun. A cepstrum is an anagram of the word "spectrum" and is a mathematical function that is the inverse Fourier transform of the logarithm of the power spectrum of a signal, The cepstrum method is a standard method for estimating the indamental frequency (and therefore period length) of a signal with fluctuating pitch. A pitch period can,, begin at any point, along a wavefbrn, provided it ends at a corresponding point,. Pitch tracking process 121 considers the starting point of each pitch period to be the primary peak or highest peak of the pitch period. Pitch tracking process 121 determines 121 e the first primary peak 77. Pitch tracking process 121 determines a single peak by taking the input waveform, sampinling the input waveform., taking the slope between each sample point and taking the point sampling point closest to zero. Pitch tracking process 121 searches several peaks wit i an expectation range and takes the peak with the largest magnitude as the subsequent primary peak 77. Pitch tracking process 121 adds 121f the prior pitch period to the primary peik. Pitch tracking process 121 determines 121g a second primary peak SI locating a nmaximuin peak from a series of peaks 79 centered a time period, P, (equal to the prior pitch period, PPc) from the first primary peak 77. The peak whose time duration from the primary peak 77 is closest to the time duration of tihe prior pitch period PPo is determined to be the ending point 25 WO 2007/130958 PCT/US2007/067906 ofthat period (PP) and the starling point of the next (P). The second primary peak is determined y analryzing three peaks before or three peaks after the prior pitch period from the primary peak and designating the largest peak of those peaks as the second peak 82. Process 121 vectorizes 121 i the pitch period. Pitch tracking processor 120 makes 121i the second primary peak the first primary peak of the next pitch period and recursively executes, eg. back to 121 f, returning a set of vectors. That is, pitch tracking process 120 designates 121j the second primary peak as the first primary peak of the subsequent pitch period and reiterates (12 1 f)-(121j). Each set of vectors correslmponds to a vectorized pitch period of the waveformn, A pitch period is vectorized by sampling the wavefonrm over that period, and assigning the sample value to the i ' coordinate of a vector in Euclidean n-dimensional space, denoted by 93 . where the index i runs frorn I to n, the number of samples per period. Each of these vectors is considered a point in the space ', FICG 14B shows an illustrative sampled wavefomn of a pitch period. The pitch period inchaudes 82 sampling points (denoted by the dots yidg on the wavefbrm and thus when the pitch period is vectorized, the pitch period can be represented as a single point in an 82 (or higher) -dimensional space. Thus, pitch trn'aeking processor 120 identifies the beginning point and ending point of each pitch period. Pitch tracking processor 120 also accounts for the variation of time between pitch periods. This temporal variance occurs over relatively long periods of time and thus there are no radical changes in pitch period length from one pitch period to the next. This iilows pitch tracking process 62 to operate recursively, using the length of the prior period as an input to determine the duration of the next. Pitch tracking processor 120 can be stated as the tbllowing recursive tfinetion: The function j.p ') operates on pairs of consecutive peaks p and p in a wavefor.m, recurring to its previous vaiue (the duration of the previous pitch period) until it finds the peak whose location in the wavebform corresponds best to that of the first peak in the wavefbrmn. This peak becomes the first peak in the next pitch period, In. the notation used here, the letter p subscripted, respectively by ")prev," "new," "next' arnid 0," denote the 26 WO 2007/130958 PCT/US2007/067906 previous, the current peak being examined, the next peak being examined, and the first peak in the iTlp.c ,etctvy he valu 'no .. inth pitch perio r: e value " denotes the time duration ofthe prior pitch period, and dp ') denotes the duration between the peaks p and p. B. Principal Component Analysis Principali component analysis is a method of calculating an orthogonal basis for a given set of data points that defines a space in which any variations in the data arc eompleey uncorrected. PA cati be used as a compression ,technique to store pi"oh periods from the pitch. tracking processor for detailed analysis. The symbol "9? "is defined by a set of n coordinate axes, each describing a dimensions or a potential for variation in the data Thus, coordinates are required to describe the position of any point. Each coordinate is a scaling coefficient along the corresponding axis, indicating the amount of variation along that axis that the point possesses. An. advantage of PCA is that a trend appearing to span mIultipie dimensions in t1 ' can be decomposed into its "principal comnponents," 1i,.e, the set of eigen-axes that most naturally describe the undelying data. By implementitng PCA, it is possible to effectively reduce the number of dimensions. Thus. the total amount of infm)nnation required to describe a data set is reduced b . using a single axis to express several correlated variations. For example,. FIG. 6A shows a graph of data points in 3 -di -mcnsions. IThe data in FIG o6B are grouped together forming trends. FIG 6B shows the principal components of the data in FIG 6A. FIG 6C shows the data redrawn in the space detennined by the orthogonal principal components. There is no visible trend in the data in Fk 6C as opposed to FIGS. 6A and 6B, In this example, the dimnnsionaliwy of the data was not reduced because of the low-dimelnsionality of the original data, For data in higher dimensions, removing the trends in the data reduces the data's di.mersionality by a factor of between 20 and 30 in routine speech applications, Thus, thc purpose of using PCA in this method of compressing speech is to describe the trends in rlh pitch ,-periods and to reduce flthe amount of data required to describe speech waveforms. Referring to FIG 15, principal components process 124 determines (1 52) the number of pitch periods generated from pitch tracking process 12 1. Principal components process 124 generates (154) a correlation matrix. The actual computation of the principal components of a waveibnn is a vell-defined mathetnatical operation, and can be understood as follows. Given two vectors x and y sy ? '2 WO 2007/130958 PCT/US2007/067906 is the square matrix obtained by multiplying x by the transpose of y. Each entry [xy' isl the product of the coordinates x and13,. Similar fly iX and Y are matrices whose rows are the vectors x? and y, respectively, the square matrix XY' is a sun of matrices of the form [xy'ly: X S'XY,= XY' can therefore be interpreted as an array of correnlation values between the entries ifn the sets of vectors arranged in X and Y. So when X=Y, XX"'is an "aoorretion matr.,ix," in which each entry [XX '], gives the average correlation (a measure o sinilarit) between the vectors x and x,. The eigenvectors of this matrix therefore dfine a set o axes in 91 corresponding to the corelationsbetween the vectors in X. The eiger-basis s the most natural basis in which to represent the data, because its orthogonality implies lthat coordinates along different axes are uncorrelated, and therefore represent variation orf different characteristics in the underdying data Princ ipal components,, process 124 detemn-ines ( 56) the principal components from the eigenvalue associated with each eigenvecto Each eigenalue measures the relative importance of the diflerenrt characteristics in the underlying data. Process 124 sorts (158) the cigenvectors in order of decreasing eigenvalue, in order to select the several mo.st important eigen-axes or "principal components" of the data. Principal components process 124 determines (160) the coefficients or each pitch period. The coordinates of each pitch period in the new space are defined by the principal components. These coordinates correspond to a projection of each pitch period onto the principal components, Thtuitively, any pitch period can be described by scalin: each principal coponent axis by the corresponding coefficient {r the given pitch period, followed y perfo, rming a suniati of these scaled vectors. Mathematii dnnaly, t e projection"s of each vectorized pitch period onto the principal components ar e obtained by vector inner products: In this notation. the vectors x and x denote a vectorized pitch period in, its initial and PCA representations, respective The vectors e, are the ith principal comp onents, and the inner product ej-x is the scaling factor associated with the ith principal component. 28 WO 2007/130958 PCT/US2007/067906 Therethr,c if any pitch period can be described simply by the scaling and str.1aining the principal components of the given set of pitch periods, then the pnncipal components and the coordinates of each period in the new space are all that is needed to reconstruct any pitch period and thus the principal components and coecents are the, compressed' form of the original heart-abeat signal. in order to reconstruct any, pitch period of n sampling points, n principal components are necessary. in the present case, the principal components are the e aenvectors of the matrix SS",. where the ith row of the matrix S is the vectorized ith pitch period in a waveforn . Usually the first 5 percent of the principal components can be used to reconstruct the data and provide greater than 97 percent accuracy. This is a general property of quas-perdic data. Thus, the present method can be used to find patterns that underlie quasi-periodic data. while poviding a concise technique to represent such data. By using a single priscipal component to express correlated variations in the data, the dimensionality of the itch periods is greatly reduced. Because of the patterns that underlie the quasi-periodicity, the number of orthogonal vectors required to closely approximate any waveform is much smaller than is apparently necessary to record the waveorn verbatim Another type of analysis is the complex wavelet transfo.rnn, as described in Dual ee Coml'~x v, 'et IcTratfrm, Ivan W. Selesnick, et al., IEEE Sign i al Processing, MNagazin 123 November 2005, which is incorporated herein in its entirety. The invention can be inmplemnented in digital electronic circuitry, or in computer hard ware. firmware. software, or in combinations thereof Apiparatus o i the invention can be mpiemnented in a computer program product tangibly embodied in a In chine-readable storage device Mr execution by a programmable processor; and mthod actions can be performed by a programmable processor executing a program of instruction to.. peribr functions of the invention by operating on input data and generating outputL The invention can be implemented advantageously in one or more computer programs that are executtable on a programmable syste including at least one . ns am.,inm haIdn tast o-n progranmmabie processor coupled to receive data and instructions from, and to transmit data and istructions to, a data storage system, at least one input device, and at least one output device. Bac, computer program can be implemented in a high-level. procedural or object oriented programming language, or in assenibly or machine e language ifdesired; and in any case, the language can be a compiled or interpreted language 9 WO 2007/130958 PCT/US2007/067906 Suitable processors include, by way of example., bothI general and special purpose microprocessors, Generally; a processor will receive instructions and data from a readonly memory aind/or a r .tdom- access memory. Generally, a computer will include one or more mass storage devices for storing data files: such devices iclude magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and optical disks. Storage devices suitable for tangibly embodying computer program instructions an data include all fvmnns of non-volatile memory, i-ncluding by way of example semiconductor memory devices, such as EPROMNI. EEPROM, and flash memory devices; magnetic disks such as intemal hard disks and removable disks; magne.to-optical disks; and CD ROM disks. Any of the foregoing can be supplemented by. or incorporated in, ASICs (application-specific integrated circuits}. A nirber of embodiments of the invention have been described. Other embodiments are within ithe scope of the following claims. .,0{

Claims

3. The device of claim I wherein instructions to process further comprises ins1ructions to: a chanel to receive a third signal representative of acoustic energy principally from a maternal heartbeat; and process the first and third electrical signals to provide an electrical sg'nal representative of acoustic en ergy principally of the fetal heartbeat and a signal of the maternal hear beat.
4. The device of claim 1 further compnrising instruIctions to: render the electrical signal representative of the fetal heartbeat on an output device.
5. The device of claim I wherein the monitor further nris es an audio speaker and the electrical signal is rendered by the speaker to produce an audio representation of the fetal heartbeat. '3d WO 2007/130958 PCT/US2007/067906 6, The device of claim I wherein the monitor further comprises: a display and the electrical signal is rendered by the display to produce representation of the fetal heartbeat 7, The device of claim I wherein the monitor farther comprises: a display and the electrical signal is rendered by the display to provide a representation of the fetal heartbeat rate.
8. The device of claim 1 further comprising: an acoustic transducer comprising a polymer that exhibits piezoelctric properties, and which converts acoustic energy into the first and second signals. 9, The device of claim 2 further comprising: three acoustic transducers each comprising a polymer that exhibits piezoelectric properties, and which converts acoustic energy into the first, second and third signals.
10. The device of claim 8 the transducer, comprises circuitry to wirelessly trnsmait data to the monitor; and the monitor further comprises: circi try to receive the wirelessly transmitted data. Ti. The device of claim 8 wherein the transducers comprises a pol iymncr sheet of polyvvinyl.dee fluoride and/or co-polymners thereof
12. A method of monitoring fetal heart beat, the method comprises: receiving over a first channel, a first signal rep resentative of acoustic energy principally fiom a maternal heartbeat; receiving, over a second channel, a second signal representative of acoustic energy including a fbtal heart beat processing the first and second electric signals into an electrical signal representing acoustic energy principally ofthe fetal heartbeat.
13. The method of claim 12 further comprises: converting acoustic energy representative of maternal uterine contractions into a third electrical signaL 32 WO 2007/130958 PCT/US2007/067906
14. The method of claim 12 wherein processing further comprises: processing the first and second electrical signals to provide the electric siga representative of acoustic energy principally of the fetal heartbeat, the seowd signa to provide a si gnal representative of the maternal heart and the third signal to provide a signal representative ofimatern.,al uterine contractions,
15. The method of claim 12 father comprising: rendering the electrical signals representative of the Jftal heartbeat, maternal heartbeat and uterine contractions on an output device. 16,. A fetaI heart monitor device comprises: a channel to receive a first signal representative of acoustic energy principally from a maternal -1 artbeat and a second signal representative of acoustic energy including a i"tal heart beat; and circuitry to process the first and second electrical signals into an elec trical, signal representing acoustic energy principaly of the fetal heartbeat.
17. The device of claim. 16 timther comprising: a channel to receive a third signal representative of acoustic energy of uterine contractions: and circuitry to process the third electrical signal imnto an indication of rnaternal uterine rates of contraction. 18 1The device of claim 16 further comprising circuitry to: re-der the electrical signal representative of the fetdal heartbeat on an. output device
19. The device of claim 16 further comprises: circuitry to modaulate the fetal heart tone into the audible frequency range; an audio speaker to remnder an audio representation of the f e tal hear beat and a display to render a visua representation of the fetal hearthat: a display to render a value indicative of fetal heartbeat rate.
20. An acoustic transducer comprises: 33 WO 2007/130958 PCT/US2007/067906 a base member; a polymer sheet having a pair of electrodes disposed over major, opposing surfaces of fe polymer sheet, the polymer sheet disposed adjacent an exterior portion of thie base member; a cap affixed to the base member and electrical circuitry carried by the acoustic transducer and coupled to the electrodes on the polymer sheet.
21. The acoustic transducer of claim 20 wherein the circuitry is disposed between the base and the cap.
22. The acoustic transducer of claim 20 wherein the cap has a convex surface. 2. The acoustic trmansducer of claim 20 wherein the cap has a convex surface and is secured to the base with s-naps.
24. The acoustic transducer of claim 20 wherein the cap and the base member are secured together with glue or weded.
25. The acoustic transducer of claim 20 wherein the cap and the base member are secured togeutier
26. The acoustic transducer of claim 20 wherein. base has an aperture and the polymer sheet is supported in the aperture by attaching a securing member to o o f the major surfces of the polymer, the one major surtbce being on an external surface of the acoustic transdoucer.
27. The acoustic transducer of claim 20 where, an exterior surfi'ce of the base member h-as an adhesive layer thereon to adhere the transducer to epidermis of a subject,
28. The acoustic transducer of claim 20 wherein an exterior surface of the base member has an adhesive layer thereon to support an outer one of the -major surfaces of the polymer and to adhere the transducer to epidermis of a subject. 34 WO 2007/130958 PCT/US2007/067906
29. The acoustic transducer of claim 20 wherein the adhesive layer provides an acoustic ipedance coupling between the outer one of the major surfaces of the polymer and epidermis of the subject.
30. Fhle acoustic transducer of claim 20 wherein the adhesive layer is a double sided tape. 1. The acoustic transducer of claim 20 wherein the circuitry comprises a transmitting device to wiredessly transmit signals from the transducer.
32. The acoustic transducer of claim 20 wherein the circuitry comprises: a low noise, high impedance ampliier coupled to receive a voltage potentied produced across electrodes of the polymer sheet; and a transmitting device coupled to the output of the amplifier to wirclessv transmit an output signal from the transducer
33. The acoustic transducer of claim 20 wherein the circuitryv comprises circuitry to couple wires or cables to output signals from the transducer.
34. The acoustic transducer of claim 20 wherein the circuitry comprises: a low noise, high impedance aiplifier coupled to receive a voltage potential produced across elctrodes of the polyler sheet; and a connector to couple signals 'om the amplifier to the wires or cables. 3. The acoustic tranrsducer of claim 26 wherein the aperture in the base member is a generally rectangular aperture in a substantial portion of the base member.
36. The acoustic transducer of claim 26 wherein, the aperture in the base member is a generally Y- shaped aperture having three regions, the aperture in a substantial portion of the o ase member; and wherein the acoustic transducer comnises: an additional pair of polymer sheets, with the polymer sheet and the addition pair of polymer sheets disposed in thle three regions of the aperture. .3 WO 2007/130958 PCT/US2007/067906 3 7 , The acoustic transducer of claim 20 wherein the base member and cover are secured together by at least one of the following: a plura.it of snap catches on one of the cover and base that mate with receptacles on the other one of the cover and base to secure the base to the cover gluing, screw fastening, and welding.
38. The acoustic transducer of claim 20 wherein the transducer hod y is a round shape.
39. The acoustic transducer of claim 20 where, the transducer is lbr hearn mnitoring.
40. The acoustic transducer of claim 20 wherein the polymer sheet is polyvinyldene fluoride andor a co-polymer thereof.
41. IThe acoustic transdutcer of claim 20 wherein the base and cover are comprised of' a relatively strong plastic material that is sufficient in strength to support- the weight of a pregnant woman.
42. The acoustic transducer of claim 20 wherein the base and cover are comprised of an ABS plastic any of a class of plastics based on acrylonitrie-butadiene styrene copolythers,
43. The acoustic transducer of claim 20 wherein the base has an aperture and the polymer rinember is disposed within the aperture of the base. 44 The acoustic transducer of claim 20 wherein the base has an aperture filled with an acoustic foam materials and the polymer member is disposed withiin the aperture of the base.
45. A.n acoustic transducer comprises: a base nmemnber having an aperture; 36 WO 2007/130958 PCT/US2007/067906 a polymer sheet comprised ofpolyvinvyldene fluoride anid/or a co-polymer thereof, the sheet havi-g a pair of electrodes disposed over majorr; opposing surfaces of the sheet with the sheet disposed in the aperture in the base member; a cap affixed to the base member; electrical circuitry disposed in the acoustic transducer and electrically coupled to the electrodes on the sheet, the circuitry comprises a transmitter to transmit signals fromn the po ,lymer sheet; a low noise, high impedance amplifier coupled to receive a voltage potential produced across electrodes of the sheet; and a transmitting device coupled to the amplifier to wire-essly transmit an outut sigai fromn the ampliftier.
46. The acoustic transducer of claim 45 wherein the cap has a conrvex surface.
47. The acoustic transducer of claim 45 wherein the sheet is sup ported in the aperture by attaching an dhesive to one of the major surfthees of the polymer, the one major surface being on an external surface of the acoustic transducer.
48. The acoustic transducer of claim 45 wherein the adhesive layer adheres the transducer to epidermis of a subject.
49. The acoustic transducer of claim 45 wherein the adhesive layer provides an acoustic impedance coupling between the outer one of the major surtfices of the polymer and epidermis of the subject.
50. The acoustic transducer of claim 45 wherein the adhesive layer is a double sided tape, 51 . The acoustic transducer of claim 45 wherein the aperture ini the base member is a generally rectangular aperture in a substantial portion of the base member,
52. The acoustic transducer of claim 45 wherein the aperture in- the base meniber is a generally Yshaped aperture having three regions, the aperture in a substantial portion, of the base member; and wherein the acoustic transducer comprises: 37 WO 2007/130958 PCT/US2007/067906 an additional pair of polymer sheets with the polymer sheet and the addition pair of polymer sheets disposed in the three regions of the aperture.
53. A method comprises: converting acoustic energy representative of a maternal heartbeat and ia fetal heartbeat into a first electrical sig al; processing the irst electrical signal to providea eecri ca signal prfiipally representative of the fetal heartbeat; and rdeten ining pitch periods of the signal principally represent tative of the fetal heart beat.
54. The method of claim 53 further comprising: convert-ing acoustic energy representative principally of a maternal heartbeat into a second electrical signal; processing the processing the first and the second electrical signals to provide the electrical sig-na lprincipally . representative of the fetal heartbeat.
55. The method of claim 53 wherein processing tIrther comp ses : rendering the electrical signal principally representative of the fetal heartbeat on an output device.
56. The method of claim 53 farther eomprising: determirning principal components of determined pitch periods of the signal principally representative of the fetal heartbeat.
57. The method of claim 53 further comprising: nodulating the electrical signal principally representative of the fetal heartbeat with a signal in the audible spectrum of human hearing.
58. The method of clim 57 wherein determining pitch, periods fi".zrther comprises; determining an initial period length value of the signal principally representative of the fetal heartbeat by finding a cepstrumn of the first few pitch periods of the signal princ.pally representative of the fetal heartbeat to determine the frequency of the signal. 38 WO 2007/130958 PCT/US2007/067906
59. The method of claim 57 wherein determining pitch periods frther comprises: deterimnining a beginning and ending point of each pitch period in the signal principally representative of the fetal heartbeat.
60. The method of claim 59 wherein determining pitch periods finther comprises: determining a variation of time durations between pitch periods; and using the length of a prior period asan input to determ-ine the duration of a subsequenit pitch period.
61. The method of claim 59 further comprising: applying principal component analysis to the determined pitch periods to compress data representing the determined pitch periods.
62. A computer program product residing on a computer readable medium f6r detecting fetal heartbeat energQy, comprises instructions to cause a monitor to: convert acoustic energy representative principally of a maternal heartbeat into a first electrical signal; convert acoustic energy representative of a maternal heartbeat and a ftal heartbeat into a second electrical signal.; process the first and second electrical to provide an electrical signal principally representative of the fetal heartbeat; and determine pitch periods of the signal principally representative of the fetal heart beat.
63. The computer program product of clainm 62 farther comprising instructions to; convert acoustic energy representative of maternal uterine contractions into a flthird elec\trical signal.
64. The computer program product of claim 62 further comprising instructions reader the electrical signal principally representative of the fetal heartbeat on an output device. 39 WO 2007/130958 PCT/US2007/067906
65. The computer program product of claim 62 further co m prising instructions to: determine principal components of determined pitch periods of the sig-nal principally representat ive of the fetal heartbeat.
66. The computer program product of claim 62 further comprising instructions to: modulate the electrical signal principally representative of the t heartbeat with a signal in the audible spectrum of human hearing.
67. The computer program product of claim 62 further comprising instructions to: determine an initial period lengh value of the signal r~npa re representative of the feal heartbeat by finding a cepstrum of the first few pitch periods of the signal principally represeontati ve of the fetal heartbeat to determin e the fiequencv of the signal.
68. 'he computer program product of claim 62 further comprising instructions to: determine a beginning and ending point of each pitch period in th.e signal principally representative of the fbtal heartbeat.
69. The computer program product of claim 62 further comprisin-g instructions to: determine a variation of time duratio ns between pitch periodss, and use the length of a prior period as an input to determine the duration of subsequent pitch period.
70. An apparatus comprises: circuitry to convert acoustic energy representative principally of a maternal heartbeat into a first electriCal signal: circuitrv to con vert acoustic energy representative of a matemal heartbeat and a ta heartbeat into a second electrical signal circuitry to process the first and second electrical to provide an electrical signal. principally representative of tlhe fe al hearteat: and circuitry to deteCjine pitch periods of the signal principally representative of the fetal heart beat. 40 WO 2007/130958 PCT/US2007/067906
71. The apparatus of claim 70 further comprising: circuitry to con vert acoustic energy representative of maternal terrine contractions intoa a third electrical signal. 7. The apparatus of claim 70 further comprising: Circuitry to render the electrical signal principally representative of the fetal heartbeat on an output device. 3, The apparatus of claim 0 further comprising: circuitry to determine principal components of determined pitch periods of the signal principally resentative of the fetal heartbeat; circuitry to modulate he electrical signal principally representative of the fietnal heartbeat with a signal in the audible spectrum of human hearing 74, The apparatus of claim 70 fuiither comprising: circuitry to determine an initial period length value of hre signal. prncipally representative of the fetal heartbeat by finding a ceps-rurn. of the first few pitch periods of the signal principally representative of the fetal heart eat to determine the frequency of the signal. 7. The apparatus of claim 70 further comprising: circuitry to determine a beginning and ending point of each pitch period in the sgnal principal ly representative c of th.e fetal heartbeat.
76. 'The apparatus of claim 70 further comprising: cirutry to determine a variation of tirne durations between pitch periods; and circuitry to use the length of a prior period as n input to determine the duration of a subsequent pitch period; and store the compressed representation of the determined pitch periods. i The apparatus of claim 70 further comprising: circuitry to determine a variation of time durations between pitch periods; and 41 WO 2007/130958 PCT/US2007/067906 circuitry to use the length of a prior period as an input to determine the duration of a subsequent pitch period; and circuitry' to apply principal component analysis to the determined pitch periods to compress data representing the determined pitch periods; and store the compressed representation of the determined pitch periods.
78. The apparatus of claim 70 further comprising: circuitry to determine a variation of time durations between pitch periods; and circuitry to use the length of a prior period as an input to determine the duration of a subsequent pitch period; and circuitry to apply principal component analysis to lthe detenrmiied pitch periods to compress data representing the determined pitch periods; circuitry to process the determined pitch periods to provide a representation; conipress the re-presentation of the determined pitch periods; and store the compressed representation of the determined pitch periods.
79. The apparatus of clahni 70 further comprising: circuitry to store a compressed representation of the determined pitch periods.
80. A method of acou stic monitoring comprises: transducing acoustic energy from a first acoustic transducer attached to a first location on a patient the acoustic energy from the first transducer, comprising desired acoustic energy to be monitored and interfering acoustic energy; transducing acoustic energy from a second acoustic transducer, attached to a second, different location on a patient, the acoustic energy from the second transducer, comprising desired acoustic energy to be monitored and interfering acoustic energy; converting the acoustic energy sensed at the first and second locations into first and second electrical siganals; processing the first and second electrical signals to digitally remove interfering acoustic energy present in the second signal to provide an electrical signal representative of the acoustic signal that is being monitored. 42 WO 2007/130958 PCT/US2007/067906
81. The method of claim 80 wherein the interfering acoustic energy is primncipall representative of a maternal heartbeat.
82. The method of claim 80 wherein the acoustic energy to be monitored includes acoustic energy representative of a fttal heartbeat; and processing the first and second electrical signals provides the electrical signal representative c of the fetal heartbeat.
813. The method of claim 80 further comprising: transducing a plurality of signals from a plurality of transducers, including the first transducer, t he plurality of signals representing the acoustic energy to be monitored; and processing the first the plurality of signals along with he second electrical signal to provide the electrical signal representative of the acoustic energy to be monitored. 84. The method of claim 83 wherein the acoustic ener gy to be monitored includes acoustic energy representative of a Ietal heartbeat; and processing the plurality of signals including the first signal, and second electrical signals provides t he electrical signal representative of the fettal heartbeat. 85. A method of monitoring health status of a Ietus, the method comprises: transducing acoustic energy from a first acoustic transducer attached to the epidermis about the vicinity of the abdomen of a pregnant woman, the acoustic energy fronim the first transducer, comprising acoustic energy of a fetal heartbeat and interlring acoustic energy of a matema heartbeat; transducing acoustic energy from a second acoustic transducer, attached to the percord.i m region of a pregnant woman, the acoustic energy from the first transducer the acoustic energy fiom the second transducer, comprising the interfering acoustic energy of the maternal heartbeat: converting the acoustic energy sensed at the first and second locations into first and second electrical signals; and processing the first and second electrical signals to provide an output signal represent tative of the etal heartbeat, 43 WO 2007/130958 PCT/US2007/067906 86. The method of claim 85 wherein the interfering acoustic energy is removed during processing of the first and second signals. 87. The method of claim 85 wherein processing further comprises: processing at least the second electrical signal to provide a second output s ig al representati-ve of the miaternial heartbeat, 88 The method ofclaim 85 wherein the second transducer is attached beneath the percrdiunm area of the patient. 89 The method of claim 85 further comprising: converting acoustic energy representative of maternal uterine contractions into a third electrical sigml. 90. The method of claim 85 thrther comprising: processing the third electrical signal to provide a sinat representative of a rate of maternal Iterine contractions. 91. , The method of claim 85 wherein the method is applied to -monitor etal heartbeats, the method further comprises: attaching the first transducer to the abdominal region of the patient in a region where the tback, of te fetus is against the maternal abdominal wait. 92. The method of claim 85 futirther comprising: rendering the electrical signal representative of the fetal he-artbeat on an output device. 93 The method of claim 92 wherein the ouatpu t device is an audio speaker. 94 The method of claim 92 wherein the, output device is a display device that renders an electrocardiogrum. 44 WO 2007/130958 PCT/US2007/067906 95. The method of claim 92 wherein the outt device is a display device that renders readout of heartbeat rate. 96. The method of claim 91 further comprising: rendering the second output sig nial representative of the matenud heartbeat oi an output device 97. The method of claim 91 wherein the acoustic trasducers are wireless. 98. The method of claim 91 wherein the acoustic transducrs are coupled to a processing device via cables and/or wires. 45