Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R25/00—Deaf-aid sets, i.e. electro-acoustic or electro-mechanical hearing aids; Electric tinnitus maskers providing an auditory perception
  • H04R25/60—Mounting or interconnection of hearing aid parts, e.g. inside tips, housings or to ossicles
  • H04R25/604—Mounting or interconnection of hearing aid parts, e.g. inside tips, housings or to ossicles of acoustic or vibrational transducers
  • H04R25/606—Mounting or interconnection of hearing aid parts, e.g. inside tips, housings or to ossicles of acoustic or vibrational transducers acting directly on the eardrum, the ossicles or the skull, e.g. mastoid, tooth, maxillary or mandibular bone, or mechanically stimulating the cochlea, e.g. at the oval window
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R2225/00—Details of deaf aids covered by H04R25/00, not provided for in any of its subgroups
  • H04R2225/67—Implantable hearing aids or parts thereof not covered by H04R25/606

Definitions

• the invention relates to an implantable sound receptor for hearing aids, especially for implants. animal hearing aids.
• a transducer is used in such hearing aids with which sound waves can be converted into electrical signals.
• Such transducers are known in the form of microphones and require a corresponding membrane, the vibration of which can be converted into electrical signals.
• the location of the attachment and, above all, the size of the membrane are of great importance for the sensitivity of such microphones.
• Sound vibrations can be recorded by pressure-sensitive membranes, as is common in the construction of microphones, or can be detected by vibrometers, with which vibrations are recorded as acceleration signals or as strain measurement signals when vibrating components are deformed.
• US Pat. No. 5,531,787 proposes accelerometers in the form of piezo-resistive vibration sensors.
• capacitive acceleration sensors for scanning sound vibrations are known.
• Such miniaturized sensors have already been proposed for implantation in the area of the middle ear, acoustic pressure waves which arise in the area of the middle ear being sensed in the form of mechanical vibrations.
• microphone constructions are relatively insensitive, since an exact match to the acoustic impedance between the sensor and the tympanic cavity of the middle ear cannot be easily achieved.
• sounds that are heard are caused by sound waves, the pitch increasing with increasing frequency and volume increasing with increasing amplitude.
• tones and sounds which represent mixtures of tones
• the sound waves are perceived, which are directed from the ear cup to the outer auditory canal and cause the eardrum to vibrate.
• the hammer handle has grown together with the eardrum, with further transmission via the ossicles through the stirrup plate to the perilymphatic fluid, which causes the Cortic organ to vibrate.
• the excitation of the hair cells in the cortic organ generates nerve impulses that the auditory nerve directs into the brain, where they are consciously perceived.
• the eardrum acts as a pressure receiver and has a diameter of approximately 1 cm. If microphones with such large membranes are to be used for recording sound waves, such microphones are hardly suitable for implantation, since the space required for this is not available in the area of the ear.
• the miniaturization of microphones leads to a reduction in sensitivity, which is due not least to the lack of matching of the acoustic impedance between the microphone and the ambient air. Even if this effect can be improved by implanting the microphone under the skin, this leads to a change in the frequency range that can be scanned, in particular higher frequencies being more strongly attenuated.
• Other mechanical sound wave receptors such as, for example, tubes filled with fluid, also lead to damping due to the viscosity of the fluid used, rigid acoustic couplers being generally unsuitable for implantation.
• the invention now aims to provide a small-scale implantable sound receptor in which the disadvantages of the known sound receptors are avoided and the acoustic sensitivity can be kept at a consistently high level over the entire frequency range essential for hearing from about 100 Hz to over 10 kHz .
• the invention further aims to keep the dimensions so small that the implantation in the middle ear and / or in the adjacent mastoid cavity is possible.
• the surgical intervention should preferably be reversible, and if the sound receptor fails, there should be no significant deterioration in the pre-existing hearing. However, depending on the actuator used and its point of application, an operational interruption of the formwork cable chain may be necessary to avoid feedback.
• an operational interruption of the formwork cable chain may be necessary to avoid feedback.
• In addition to these requirements for one implantable sound receptor should naturally also keep the energy consumption of the sound receptor and a subsequent evaluation circuit so low that the miniaturization enables a total implantation.
• the implantable sound receptor according to the invention for implantable hearing aids essentially consists in the sound sensor being designed as an optical sensor for vibration or distance measurements and being arranged in the ear at a distance from the surface of a part of the sound transmission which can be excited by acoustic vibrations.
• the contactless design prevents undesirable side effects of damping such vibrating ossicles or the eardrum and allows the relatively large vibration absorption area of the eardrum to be used unhindered for the measurement, so that a much higher sensitivity can actually be achieved than would be possible with correspondingly smaller membranes.
• the fact that the optical sensor is arranged or can be arranged at a distance from the surface of a part of the vibration transmission which can be excited to vibrate ensures that damping of the vibration of such parts of the vibration transmission which can be excited by vibration can be excluded with certainty and the use of optical sensors allows the use of extremely small sensors.
• Optical sensors are to be understood here as sensors which do not necessarily use visible light.
• electromagnetic waves can be used in a relatively wide frequency range, which goes beyond the spectrum of visible light.
• Transmitter laser diodes are used in the infrared and ultraviolet range of the radiation as well as in the visible range, as long as the vibrating surface to be measured is sufficiently reflective in the range of the incident wavelength.
• Optical sensors are therefore primarily used to measure the optical parameters of the reflected components of the emitted signal, with an advantageous procedure for evaluating the signals of the sound receptor such that the optical sensor is used with an interferometer for evaluating the amplitude, frequency and / or the relative phase position of the vibration of the scanned part is connected.
• the use of the interferometer principle allows contactless detection of even small amplitudes of natural vibrations in the area of the ossicles.
• the range to be recorded here ranges from amplitudes of 10 -11 m to about 10 -5 m, amplitudes higher than about 5x10 "5 m, as can be observed with sound radiation of about 120 dB, generally not for further measurements come into consideration, since they are already likely to damage the inner ear.
• the vibration of the ossicles and the eardrum, as observed when stimulated by acoustic waves, is however also superimposed on the ear by a low-frequency, quasi-static or slow displacement of the eardrum membrane and the ossicles, which can be attributed to differences in air pressure or pressure in the inner ear .
• Such low-frequency shifts are caused, for example, by changing the air pressure when driving in elevators, cable cars or airplanes, with significant low-frequency fluctuations being observed by the sudden opening of the Eustachian tube even when blowing.
• Such low-frequency shifts can be at least 10 ⁇ higher in amplitude than the maximum amplitudes that occur in physiological sound.
• Optical sensors must now be arranged so that even with such displacements there is no contact with the part to be scanned and the design according to the invention is therefore such that the optical sensor is arranged at a distance from the scanned part which is greater than the maximum displacement of the scanned part in the direction of the sensor and / or at a collision-preventing distance.
• the use of an adjustable holder to maintain a defined distance can comprise a servo motor, the control signals of the control motor being used for the determination of the acoustic vibrations, and the control movements themselves being triggered by the optical sensor.
• Optical scanning is achieved in a particularly simple manner in that the optical sensor interacts with at least one light or laser diode and the reflected signals are fed to an electronic evaluation circuit via fibers of waveguides, in particular optical fibers, of at least one optoelectronic coupling component, for example a photodiode.
• the part of the sensor to be implanted in the middle ear or the epitympanon or parapet is restricted to the relatively small free end of the optical waveguide, via which the optical signals are fed in and the reflected signals are removed.
• one or more optical systems such as, for example, lenses, beam splitters, prisms, mirrors or the like, can of course also be arranged in the beam path in order to precisely specify or localize the measurement.
• the evaluation circuit must subsequently provide a correspondingly amplified signal for the stimulus of the auditory nerve, the training here being advantageously made such that the evaluation circuit signals for electromechanical vibration generator and / or for the electrical stimulation of the cortic organ and / or the auditory nerve and / or the brain stem and has connections for corresponding signal lines.
• the design is advantageously made such that the free ends of the optical sensor are provided with a coating which inhibits cell growth are.
• the evaluation circuit is supplied with at least two signals for determining the phase position, the determination of the phase position in a known manner depending on the type of interferometer used and the selected circuit arrangement of the evaluation circuit enabling corresponding active or passive stabilization.
• a working point specified by a defined distance from the surface to be measured applies to the optimal sensitivity of the optical sensor.
• Low-frequency displacements of the parts to be scanned can of course lead to the fact that this optimum working point is left or even a phase shift or phase reversal occurs.
• These undesirable side effects, which result in a "fading" of the measured signal can advantageously be eliminated in that the evaluation circuit contains a stabilizer circuit to compensate for the shift in the operating point of the interferometer by low-frequency shifts in the scanned part.
• appropriate compensation can be ensured by additionally providing a sensor for determining the distance of the part to be scanned from the optical sensor.
• Interferometric signals can be stabilized in a particularly simple manner by comparison with a reference signal or by measuring a plurality of signals, with polarizing beam splitters being switched on in the beam path can and the signals can be detected independently and by different photodiodes.
• Conclusions about the correct phase position can also be derived from a mathematical analysis of the measurement signal form, for which purpose frequency comparisons and in particular the evaluation of higher-order vibrations in the stabilizer circuit can be used.
• the design is made in a particularly simple manner so that the free end of the optical sensor is adjustably fixed in a bearing block and / or is connected to an adjusting drive, as a result of which an exact orientation and exact positioning relative to the surface of that part can be ensured, the vibration of which is to be measured.
• Interferometers can be of any design, such as Michelson, Fabry-Perot or Fizeau interferometers, with suitable stabilization algorithms, for example, in the article by KP Koo, AB Tveten, A. Dandridge, "Passive stabilization scheme for fiber interferometers using (3x3) fiber directinal couplers ", in Appl.Phys.Lett. , Vol. 41, No .7, pp. 616-618, 1982, G. Schmitt, W. Wenzel, K.
• FIG. 1 shows a cross section through the human ear, in which the arrangement of the sensor in the middle ear area or in the attic is shown
• FIG. 2 shows a block diagram for a totally implantable hearing aid
• FIG. 3 shows a schematically illustrated holder for the waveguide or for the waveguide encased in a rigid sleeve in the mastoid cavity.
• Fig. 1 the ear of an ear is designated 1. Sound vibrations subsequently reach the membrane labeled 2, namely the eardrum with which the ossicles interact. The ossicles are referred to together with the reference number 3.
• the ossicles are located in the middle ear.
• the cochlea is labeled 4.
• the non-contact sensor for sensing the vibrations from the ossicle 3 is implanted in the mastoid cavity and its tip protrudes into the attic space or into the middle ear via the drilled chorda-facial angle. It has a free end 5 which is inserted in a stable sleeve (casing) which is held in a bearing block 6 so that it can be oriented.
• the bearing block 6 can be fixed in the mastoid cavity or the surrounding cranial bone, the free end of the optical sensor essentially consisting of the free end of an optical fiber or waveguide 7.
• the tip advantageously contains an optical system, for example lenses, beam guides, prisms, mirrors or the like.
• the optical waveguide 7 is connected to an optoelectronic evaluation circuit 8, in which an interferometer 9 is arranged.
• the optoelectronic evaluation circuit 8 can additionally contain an energy supply in the form of a battery in its housing, the circuit arrangement containing corresponding input-output circuits, correspondingly containing hearing aid electronics for signal processing, noise suppression, acoustic limitation, etc. or these circuits required for the actuator are housed in their own implantable part, which is coupled with an electrical cable. The electrical signals thereof can be transmitted to the cochlea 4 via the lines 10.
• this optoelectronic evaluation circuit can also be completely implanted.
• the type of forwarding of the evaluated signals to the inner ear or the auditory nerve is of secondary importance for the type of scanning of the vibrations.
• the actuator can be one that sets auditory ossicles or the perilymph directly in acoustic vibrations or a cochlear implant that electrically irritates the auditory nerve or a brainstem implant that directly irritates the brain stem.
• FIG. 2 A block diagram of the circuit arrangement selected in this context can be seen in FIG. 2.
• the skin that covers the implant is indicated schematically by 11, the evaluation circuit and, in all cases, the energy supply being accommodated subcutaneously in the region of the middle ear, the mastoid cavity or on the skull bone.
• the battery is shown schematically with 12, the optical sensor and the interferometer with 13, the evaluation electronics with 14 and the actuation component, via which the signals after processing in the hearing aid electronics to an electromechanical amplifier of the perilymph vibrations or to a cochlear implant or a brain stem implant (with 15 designated) arrive.
• the energy supply by the battery 12 can preferably be provided by a rechargeable battery, for which additional inputs are provided for an induction coil 17, via which an external charging or control unit 18 enables the battery to be recharged and, if appropriate, the programming of the electronics.
• the transmission can be carried out contactlessly via an induction coil 19 of the control and charging unit 18 which can be coupled to the subcutaneous induction coil 17.
• the displaceable slide 21 carries a ball pin 22, on which a clamp with jaws 23 and 24 is fixed by means of a clamping screw 25.
• the jaws 23 and 24 here have spherical bearing surfaces which can be pivotably oriented on the circumference of the ball 26 of the ball pin 22, so that an exact adjustment in different spatial coordinates is made possible.
• an optical waveguide 27 is brought into a defined position, the free end 28 of which is oriented such that it can receive the reflected radiation from a vibrating part of the inner ear.
• optical systems, prisms, mirrors or the like can be accommodated for deflecting the beam path, if this is desired.
• the signals pass through the optical waveguide 27 to the optoelectronic evaluation circuit, which contains the interferometer.

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• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Otolaryngology (AREA)
• Neurosurgery (AREA)
• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• Prostheses (AREA)
• Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
• Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)
• Materials For Medical Uses (AREA)

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• 1998
  • 1998-10-23 AT AT0178798A patent/AT408607B/de not_active IP Right Cessation
• 1999
  • 1999-10-20 DK DK99953416T patent/DK1123635T3/da active
  • 1999-10-20 EP EP99953416A patent/EP1123635B1/fr not_active Expired - Lifetime
  • 1999-10-20 ES ES99953416T patent/ES2174644T3/es not_active Expired - Lifetime
  • 1999-10-20 AT AT99953416T patent/ATE215294T1/de active
  • 1999-10-20 US US09/830,195 patent/US6491644B1/en not_active Expired - Fee Related
  • 1999-10-20 WO PCT/AT1999/000253 patent/WO2000025550A2/fr not_active Ceased
  • 1999-10-20 AU AU10177/00A patent/AU755935B2/en not_active Ceased
  • 1999-10-20 DE DE59901093T patent/DE59901093D1/de not_active Expired - Lifetime

Non-Patent Citations (1)

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