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EP2636225A2 - Dispositif, système et procédé audio - Google Patents

Dispositif, système et procédé audio

Info

Publication number
EP2636225A2
EP2636225A2 EP11838808.1A EP11838808A EP2636225A2 EP 2636225 A2 EP2636225 A2 EP 2636225A2 EP 11838808 A EP11838808 A EP 11838808A EP 2636225 A2 EP2636225 A2 EP 2636225A2
Authority
EP
European Patent Office
Prior art keywords
ear
sound
pressure
sidewall
volume
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP11838808.1A
Other languages
German (de)
English (en)
Inventor
Stephen D. Ambrose
Samuel P. Gido
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Asius Technologies LLC
Original Assignee
Asius Technologies LLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Asius Technologies LLC filed Critical Asius Technologies LLC
Publication of EP2636225A2 publication Critical patent/EP2636225A2/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/10—Earpieces; Attachments therefor ; Earphones; Monophonic headphones
    • H04R1/1016—Earpieces of the intra-aural type
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/10—Earpieces; Attachments therefor ; Earphones; Monophonic headphones
    • H04R1/1008—Earpieces of the supra-aural or circum-aural type
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R11/00—Transducers of moving-armature or moving-core type
    • H04R11/02—Loudspeakers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2400/00—Loudspeakers
    • H04R2400/01—Transducers used as a loudspeaker to generate sound aswell as a microphone to detect sound
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2460/00—Details of hearing devices, i.e. of ear- or headphones covered by H04R1/10 or H04R5/033 but not provided for in any of their subgroups, or of hearing aids covered by H04R25/00 but not provided for in any of its subgroups
    • H04R2460/11—Aspects relating to vents, e.g. shape, orientation, acoustic properties in ear tips of hearing devices to prevent occlusion
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2460/00—Details of hearing devices, i.e. of ear- or headphones covered by H04R1/10 or H04R5/033 but not provided for in any of their subgroups, or of hearing aids covered by H04R25/00 but not provided for in any of its subgroups
    • H04R2460/15—Determination of the acoustic seal of ear moulds or ear tips of hearing devices

Definitions

  • the present device, system and methods relate to the structure, operation and manufacture of an insertable sound transmission instrument for a user's ear. Specifically, the device and methods relate to such a sound delivery instrument which can be coupled with any number of electronic sound devices, such as a hearing aid, MP3 player,
  • Bluetooth® device computer, phone, and the like, while providing improved comfort and control to the user.
  • the listener might be asked (or admonished) to turn down their headphones for the sake of their own health and for the courtesy to others, but what has not been hitherto widely realized is that the person listening to the headphones has already, unknowingly turned down their own personal perception of the volume through a natural hearing protection mechanism known as the "Stapedius reflex.”
  • Stapedius reflex a natural hearing protection mechanism known as the "Stapedius reflex.”
  • the persistent triggering of this reflex by insert headphones, hearing aids, and the like, perpetuates a vicious cycle in which even more volume may be needed to counteract the effects of the stapedius reflex.
  • the persistent triggering of the stapedius reflex also sets up an additional dangerous situation: i.e., the listener, who is already tolerating very loud volumes because of the stapedius reflex, accidentally or intentionally turns the volume up even more. At this point the stapedius muscle may already have become exhausted or reached a limit of its inherent ability to protect the ear from loud sounds and temporary or even permanent hearing loss.
  • the acoustic, standing waves produced from a speaker in the ear canal are physically and mathematically equivalent to a static pressure, akin to the air pressure confined within an inflated balloon or the static pressure employed in tympanometry.
  • the magnitude of this static pressure in the sealed ear canal is, unlike the static pressures normally encountered, oscillating at acoustic frequencies.
  • This oscillating static pressure results from the trapping of a closed volume of air in the ear canal when the sound producing device is sealed in the ear.
  • the oscillating static pressure is responsible for gross over-excursions of the tympanic membrane (ear drum) that can be one hundred, one thousand or more times greater than the normal oscillations of the ear drum associated with sound transmitted through the open air.
  • the open-air acoustical wave spectrum can contain the superposition of different sound waves at different frequencies
  • the corresponding static pressure oscillations in a sealed volume such as the ear canal, superpose to form a spectrum of coexisting static pressure oscillations with a range of frequencies.
  • TVIG Trapped Volume Insertion Gain
  • SPL sound pressure level
  • TVIG is defined as the increase in sound pressure level (SPL), resulting from the static pressure oscillations in the ear canal across all frequencies, occurs when a speaker containing device is sealed in the ear. It is measured relative to the SPL in the ear canal when the device is held in approximately the same position at the entrance to the ear canal, but is not sealed with an air-tight seal. In this unsealed reference state, the sound waves in the ear are not equivalent to static pressures. It is shown herein that the trapped volume insertion gain of insert headphones or hearing aids is often sufficient to boost the SPL experienced by the listener above the threshold at which the stapedius reflex reduces hearing sensitivity.
  • the present application addresses the need for an in-ear listening device to lessen the impact of tympanic membrane over-excursions, oscillating static pressure in the ear canal, trapped volume insertion gain, and the constant triggering of the stapedius reflex.
  • the inventive technology disclosed is applicable to ear buds, headphones, hearing aids, Bluetooth headsets and the like. The technology mitigates the detrimental effects of sealing a sound producing device in the ear canal by the use of an inflatable in-ear bubble-seal of the type claimed in our previous patent applications.
  • this application discloses a new inventive approach and a family of resultant devices that achieve the mitigation of trapped volume insertion gain, oscillating static pressure, tympanic membrane over-excursions, and the stapedius reflex in a simple and potentially inexpensive retrofit to existing in-ear devices.
  • Both the inflatable ear seals, and the retrofit devices operate to at least partially transform the sound energy in the trapped volume in the ear canal from an oscillating static pressure back into a normal acoustic wave, which is lower in amplitude and less punishing in its effects on the ear drum, the stapedius muscle, and the ear in general.
  • a vibrating surface such as a speaker diaphragm
  • the amplitude of the oscillating pressure wave that results is directly proportional to the maximum transverse velocity of the surface.
  • this maximum velocity occurs at the mid-point of the surface's oscillation, where displacement is zero and speed is greatest.
  • the loudness of sound from a speaker in open air is determined by how rapidly the surface can be made to move at its fastest point, not by the total amplitude of the excursions of the surface.
  • the amplitude of speaker motion can be seen to obviously increase. In fact, for a sinusoidal profile of speaker displacement vs.
  • the maximum speed of speaker motion can easily be shown to be equal to coL, where ⁇ is the angular frequency (2 ⁇ time frequency) and L is the maximum extent of the speaker motion. This is a secondary effect, however; these large excursions are not directly responsible for the increase in sound volume.
  • the speaker surface and its underlying electromagnetic drive are physical objects with mass and inertia, and therefore greater speed requires more distance to accelerate, and then to slow down and reverse direction at the extremes (greatest amplitude and zero velocity) of the cyclical motion.
  • the amplitude or distance of the speaker motion, L is not responsible for sound generation since a surface can move slowly over large distances (like picking up a speaker and carrying it across a room) without creating sound waves.
  • FIG. 1 shows the length of the trapped volume as a fraction of the wavelength of sound across the frequency range. Especially for low frequencies, but extending up into the mid- range, the trapped volume in the ear canal is only a small fraction of the wavelength of the sound.
  • the static pressure in the ear canal is the pressure that results from a change in the volume (a compression or rarefaction) of a fixed amount of air trapped in the ear canal.
  • This static pressure may, at any instant, be greater than, equal to, or less than the barometric pressure outside the ear.
  • the static pressure may be changing (oscillating) rapidly, and thus the use of the term static may seem strange.
  • the term static refers to the fact that this pressure is not a transient oscillation in pressure (i.e. a sound wave in open air) but rather is a thermodynamic, equilibrium property of the air mass associated with its volume. If the volume of this fixed mass of air is held constant (i.e.
  • u is the piston speed
  • p is the density of air
  • c is the speed of sound
  • / is the tube length
  • x is the coordinate along the tube from zero at the piston's zero displacement position up to /.
  • k is 2 ⁇ / ⁇ , where ⁇ is the wavelength.
  • the "o" subscripts on the u and p values indicate the use of root-mean-square (rms) values and the equations then yield rms pressures.
  • the equations apply equally well to peak valves (drop the subscripts) and then give peak pressure (i.e., amplitude of the pressure oscillations).
  • the term j is an imaginary number, also frequently known as . Disregarding the / ' , which has to do with getting the correct phase of the time oscillation, Equation 2.48 gives the amplitude of the resulting pressure wave in the tube as a function of distance x, along the tube.
  • FIG. 4 shows the pressure profiles along a 1 cm long tube, approximating the length of the sealed, trapped volume in the ear canal calculated from Beranek's equations.
  • the pressures plotted are the ratios of the amplitude (maximum value) of the pressures in the sealed tube divided by the pressure amplitude of the sound waves that the same piston motion would produce in open air.
  • the pressure in the small closed tube is significantly higher than in open air, except at high frequencies. This graph shows that at an instant in time that the pressure is very uniform along the 1 cm length of the tube.
  • FIG. 4 shows the profile at the time when pressure is maximum.
  • the pressure profile is equally flat with distance along the tube, but at other pressure levels, at other points in the time oscillation.
  • the small length of the tube, relative to the wavelength of the oscillations means that the pressure profile across the tube equilibrates at each time much faster than the overall pressure level is changing with time as a result of the piston oscillations.
  • the pressure across the tube can be considered constant at any instant.
  • Beranek's model of acoustical waves in a closed, rigid cylinder shows that the pressure waves produced by the oscillating piston, at one end, interfere with waves reflected off the opposite end of the tube.
  • the resultant pressure profile in the tube is the standing wave pattern associated with the interference of this forward and reflected wave.
  • the pressure profiles plotted in FIG. 4, resulting from this model show that in the case where the tube is a small fraction of the wavelength of the sound, that the standing pressure waves yield a flat pressure profile across the tube. There are no nodes and antinodes of high and low pressure of the type Beranek plots in his FIG. 2.6, if the tube length is very short.
  • Equation 2 The maximum speed of the piston, u, is equal to ⁇ , where ⁇ is the maximum displacement of the piston.
  • the total volume of the tube, V is equal to SI, where S is the cross-sectional area of the tube.
  • the change in volume of the tube, AV is equal to S5.
  • (S/l) is equal to (AV/V), the factor of S cancelling out of the numerator and denominator.
  • c 2 B/p, where B is the bulk modulus (resistance to change in volume). Therefore:
  • Equation 4 is the very definition of the pressure vs. volume change properties of a gas undergoing a static pressure compression or rarefaction. This has been derived, starting from an acoustical equation and imposing the limit of small tube length relative to wavelength. This proves that in this limit, we can safely analyze the case of a speaker sealed in the ear canal in terms of its static pressure effects.
  • a further insight links the reflection of the sound wave at the rigid back wall of the sealed tube, in Beranek's acoustical derivation, with the concept of static pressure.
  • the rigid boundary of opposite end of the tube can either be thought of as a wall which limits the volume change of the tube at its far end, and thus enables the piston to produce a AV, or it can be considered a hard wall boundary condition, which reflects an acoustical wave and sends a reverse wave back down the tube.
  • the result of either analysis is exactly the same for a small tube length.
  • a speaker sealed in ear canal operates like pneumatic piston, producing time oscillations in overall or static pressure (analogous to barometric pressure in open air) in the trapped volume of the ear canal. These static pressure oscillations certainly do move the tympanic membrane.
  • the peak oscillating static pressure is determined not by the maximum speaker diaphragm speed (as in the case of open air acoustic waves) but by the maximum speaker excursion, Sin Equation 3. This is, in fact, exactly the opposite of the open air operation of the speaker. However, this is also obviously true for the sealed volume case.
  • the phenomena occurring in a small trapped volume has a dual character, somewhat akin to the wave-particle dual character of light, and fundamental physical particles.
  • the oscillating pressure effects in the sealed ear canal are both acoustical waves and static pressure oscillations at the same time. Which of these two aspects of the phenomena is dominant, depends on the conditions. For instance, smaller confined volumes and lower frequencies (longer wavelengths) favor an oscillating-static-pressure-like behavior, while larger trapped volumes and higher frequencies favor an acoustical-wave-like behavior.
  • the criterion is expressed as the ratio of the length scale associated with pressure equilibration, /, to the length scale associated with pressure variation, ⁇ , due to sound. Exactly the same criterion can also be expressed as the ratio of the time scale of pressure equilibration in trapped volume to the time of sound wave pressure variation, or Iv/c). Here is the frequency.
  • FIG. 5 Gross over-excursions of the tympanic membrane have been directly observed and video of them has been recorded using the device shown in FIG. 5.
  • This device is a modification of a digital, pneumatic, video otoscope, an instrument a doctor uses to look into an ear canal.
  • a commercial Apple iPod ear-bud was sealed into the insufflation port, which is a hole in the side of the device (see FIG. 5b).
  • the otoscope When the otoscope is inserted tightly into the ear canal (FIG. 5c), it produces a trapped volume and allows the tympanic membrane to be observed and filmed while music or tones are played through the ear-bud.
  • the ear-bud on the side of the otoscope is mounted at a right angle to the snout of the otoscope, which is inserted into the ear canal.
  • the ear-bud is not projecting its sound down the ear canal but transverse to the ear canal.
  • frequencies are played through this ear-bud, there is a marked difference in how they sound when the otoscope is sealed in the ear and when the snout of the otoscope is loosened to break the seal.
  • the sound is not as distinct. It becomes louder, but also harsher (more percussive on the tympanic membrane), when the ear canal seal is established.
  • FIG. 6 A very simple model, shown in FIG. 6, was analyzed mathematically to get an initial indication of the order of magnitude of responses and the general trends associated with the static pressure effects of sealing a speaker in the ear canal.
  • This model consists of a tube of length and diameter intended to approximate the dimensions of the trapped volume in the ear canal. It is taken to be 7 mm in diameter and the length, L (the same parameter as / used in Beranek), can be varied to simulate different speaker insertion depths resulting in different trapped volume sizes. Tube lengths of 1.0 and 0.5 cm were used for illustrative calculations. One end of the tube is covered by a flexible membrane which can be displaced to simulate the motion of the speaker diaphragm.
  • E (Young's Modulus) 3 N/m 2 .
  • Both the speaker diaphragm and the tympanic membrane are assumed to have the same diameter as the tube.
  • the pressure outside the sealed tube is initially atmospheric pressure.
  • On the other side of the tympanic membrane is another volume, which simulates that of the middle ear. This middle ear volume is also initially at atmospheric pressure, and it has a volume of 1.5 cm 3 , an average value for the human population.
  • the computational model is very similar to an actual physical model of the ear canal used in recently reported experiments on the acoustics of insert headphones.
  • the model system distributes the effect of this disturbance between the pressurization of air in the sealed volume of the ear canal and the displacement of the tympanic membrane.
  • the displacement of the tympanic membrane also displaces and pressurizes air in the middle ear cavity.
  • the pressurization of the air in the ear canal and in the middle ear volume is resisted by the compressibility modulus of the air, which is derived from the Ideal Gas Law.
  • the Ideal Gas Law is an excellent representation of the behavior of air at body temperature and near atmospheric pressure, as the compressibility factor (Z) is essentially equal to one.
  • the stretching of the tympanic membrane due to the pressure differential between the sealed ear canal volume and the middle ear volume, is resisted by the stretching modulus of the tympanic membrane, and is modeled as in Reference.
  • the actual vibrational modes and extensional geometries of the tympanic membrane may be quite complex. They are simpler and more similar to the simple hemispherical deformation model used here, at lower frequencies. This modeling yields a relationship between the displacement of the tympanic membrane and the pressure difference across the membrane.
  • Equating the pressure difference across the tympanic membrane, in terms of the pressures in the ear canal and the middle ear, to the pressure driving force for deformation of the tympanic membrane allows one to solve for both the pressure increase in the trapped volume of the ear canal and extent of deformation of the tympanic membrane.
  • FIG. 7 shows the calculated tympanic membrane displacement vs. speaker displacement, for the sealed ear case, with trapped volume lengths of 1 cm and 0.5 cm. Note that there is no frequency dependence of the tympanic membrane displacement since the displacement depends on static pressure, which is related to speaker displacement, not to speaker velocity.
  • Speaker displacements in the micron range produce static-pressure-driven, tympanic membrane excursions that are also in the micron range, these are 100 to 1000 time the normal tympanic membrane excursion amplitudes, which are tens to hundreds of nanometers.
  • FIG. 8 shows the same tympanic membrane displacement vs. speaker displacement except that the tympanic membrane displacement is shown as a percentage relative to the driving speaker displacement.
  • FIG. 9 shows the SPL values that the same speaker motions would produce in open air for three different frequencies ( 10, 100, and 1000 Hz). Clearly, the larger speaker displacements produce louder sound. The speaker motions in this study would give open air SPL values that span the range from normal conversation to a jet engine.
  • FIG. 10 shows the peak sound pressure (not rms average) for open air sound and the static pressure oscillation amplitude for the sealed ear canal, as a percentage of atmospheric pressure.
  • FIG. 11 shows the same data as FIG. 10 in a different way.
  • the ratio of the sealed volume static pressure to the corresponding open air peak sound pressure is plotted vs. speaker displacement.
  • this ratio exceeds 1.0, the sealed volume pressure in the ear is greater than the corresponding open air peak sound pressure.
  • the pressures shown in FIG. 4 for a trapped volume with completely rigid walls provide a comparison to FIG. 11.
  • the pressures in a completely rigid piston are seen to be considerably higher than the ear canal with its compliant tympanic membrane.
  • the model of the previous section is an oversimplification.
  • the ear canal is not a smooth, straight tube.
  • the tympanic membrane is not flat, but rather an asymmetric, shallow, conical shape.
  • the speaker diaphragm is usually not a flat surface, and the tympanic membrane has different modes of deformation beyond the biaxial stretching used in the simple model.
  • Wada, obayashi and co-workers have done extensive measurements and mechanical modeling of different components of the human middle ear. They show that excursions of the tympanic membrane involve deformation not just of the tympanic membrane itself, but also of the connection between the tympanic membrane and the ear canal, and of the ossicular chain, which connects the tympanic membrane to the cochlea. They have determined mechanical moduli associated with these other aspects of tympanic membrane deformation, which are included in the model described in this section.
  • Modeling of the static pressure effects with a speaker sealed in the ear depends only on the net change in trapped volume associated with the combined motions of the speaker diaphragm and the tympanic membrane. These changes depend on speaker and tympanic membrane geometry, but not on the ear canal geometry, since the morphology of the ear canal along the trapped volume remains the same as the volume changes.
  • the other piece of information required to do the model calculation is the resistance to deformation of the tympanic membrane, including all the modes of deformation and the resistance to deformation of structures attached to the tympanic membrane that must move with it.
  • the model is evaluated, for a given speaker displacement, by setting the pressure difference between the trapped volume in the ear canal and the pressure in the middle ear volume equal to the pressure across the deformed tympanic membrane (now including deformation of the attachment of the tympanic membrane and of the ossicular chain).
  • the model is solved numerically, and in addition to the total displacement of the tympanic membrane, it yields an estimate of the amount of this displacement that occurs due to stretching of the tympanic membrane vs. due to motion at the attachment of the tympanic membrane to the ear canal.
  • FIG. 12 shows total tympanic membrane displacement vs. speaker displacement. This can be compared with FIG. 7 of the simpler model. The trend is the same, tympanic membrane displacement is in the multiple micron range and goes up with increasing speaker displacement. There is a slight decrease in the tympanic membrane displacement for the detailed model (FIG. 12) over the simple model (FIG. 7) because the detailed model includes additional resistance to deformation associated with the ossicular chain.
  • FIG. 13 shows the same tympanic membrane displacement vs. speaker displacement data as FIG. 12 except that the tympanic membrane displacement is shown as a percentage relative to the driving speaker displacement. This can be compared to FIG. 8 for the simple model.
  • the simple model (FIG. 8) indicated that at small speaker displacements that the tympanic membrane to speaker membrane was nearly one-to-one, and as the speaker displacement increased the percentage of that motion transferred to the tympanic membrane dropped off considerably.
  • the detailed model (FIG. 13) amends that view and shows that the percentage of speaker displacement transferred to tympanic membrane displacement is less than 50% for small speaker motions and, while it drops with increasing speaker displacement, the drop is slight.
  • FIG. 14 shows the percentage of total tympanic membrane displacement which is due to stretching of the tympanic membrane, as opposed to motion at the connection of the tympanic membrane with the ear canal. Stretching of the tympanic membrane is clearly the dominant mode of deformation, although the displacement at its connection around its edges increases slightly as the speaker displacement gets large.
  • FIG. 15 shows the peak sound pressure (not rms average) for open air and the static pressure for the sealed ear canal volume as a percentage of atmospheric pressure. This can be compared to FIG. 10 for the simple model. For the open air case, even speaker displacements producing extremely high SPL, result in peak sound pressures which are a small fraction of atmospheric pressure. The pressure in the trapped volume at corresponding speaker displacements is higher at all speaker displacements than open air peak sound pressure level.
  • FIG. 16 shows the maximum static pressure that would be generated in the trapped volume of the ear canal, by the speaker motion, if the tympanic membrane were not allowed to move (similar to Beranek' s completely rigid, sealed tube in Section 2.1 , above). These pressures are about double the pressures in FIG. 15 for the more realistic situation in which the tympanic membrane can move.
  • the maximum pressures in FIG. 16 are important reference valves because they indicate the full magnitude of the static pressure driving force that is displacing the tympanic membrane. This pressure is not realized, however, because the tympanic membrane is already moving and relieving some of this static pressure before the speaker reaches its full displacement.
  • FIG. 17 shows the same data as FIG.s 15 and 16 in a different way.
  • the ratio of the sealed ear canal static pressure to the corresponding open air peak sound pressure is plotted vs. speaker displacement. This can be compared to FIG. 11 for the simple model and to FIG. 4 for Beranek's sealed tube.
  • the sealed volume pressure is higher than the open air peak sound pressure across the entire range of speaker displacements.
  • the maximum pressures that would occur if the tympanic membrane could not move are seen to always be larger than the actual pressure.
  • the maximum pressure values agree very well with those given by Beranek's acoustical analysis of a sealed tube.
  • m is the mass of the tympanic membrane and other structures to which it is attached and which must move with it.
  • the damping parameter ⁇ includes the damping influences of the tympanic membrane as well as the structures attached to it.
  • the spring constant, k includes the spring like resistance to displacement of the tympanic membrane and the structures attached to it. The displacement of the tympanic membrane at any given time, t, is given by the parameter ⁇ .
  • the first term on the left-hand-side of this equation represents Newton' s law that force is equal to mass times acceleration.
  • the second term adds the influence of damping or resistance, which is proportional to velocity. There is more resistance the faster one tries to move the tympanic membrane.
  • the final term on the left-hand side gives the restoring, spring like, force associated with motion of the tympanic membrane.
  • This equation has the form of forced mechanical vibrations with damping.
  • the forcing function is provided by the oscillation of the speaker diaphragm, as transmitted to the tympanic membrane through the air in the trapped volume.
  • This driving function (right- hand-side of Equation 5) is represented by a sine wave with angular frequency (Wartime the sound frequency) ⁇ , and an amplitude given by the product of S, the area of the tympanic membrane, and P, the pressure which drives the motion.
  • the driving pressure is the hypothetical maximum static pressure calculated in the previous section for various diaphragm displacements when the tympanic membrane is not allowed to move. This represents the total pressure driving force available to cause the motion of the tympanic membrane as governed by Equation 5.
  • Equation 5 yields values for the amplitude of tympanic membrane displacement, ⁇ , as well as the phase lag of tympanic membrane vibration relative to the oscillation of the driving (speaker) pressure.
  • FIG. 18 shows tympanic membrane displacements in microns vs. frequency for the range of speaker displacements ranging from 1 micron to 400 microns for a 1 cm long trapped volume.
  • the tympanic membrane displacements which are on the order of microns to tens or hundreds of microns increase with speaker displacement, and are nearly constant for frequencies from 10 to 100 Hz.
  • the values in this range are about the same as those obtained with the detailed static pressure model for the same speaker displacements (FIG. 12).
  • the static pressure model does not contain a frequency dependence and is expected to be most similar to the dynamic model of this section at low frequencies.
  • FIG. 19 shows tympanic membrane displacements in microns vs. frequency for the range of speaker displacements ranging from 1 micron to 400 microns for a 0.5 cm long trapped volume.
  • the tympanic membrane displacements which are on the order of microns to tens or hundreds of microns increase with speaker displacement, and are nearly constant for frequencies from 10 to 100 Hz.
  • the values in this range are about the same as those obtained with the detailed static pressure model for the same speaker displacements (FIG. 12).
  • the static pressure model does not contain a frequency dependence and is expected to be most similar to the dynamic model of this section at low frequencies.
  • FIGS. 18 and 19 show that at frequencies between 100 and 1000 Hz that the displacement starts to fall off with increasing frequency. This is due to the fact that at higher frequencies, inertial effects prevent the tympanic membrane and its associated structures from fully responding to the driving force before that force changes in magnitude and/or direction.
  • FIG. 20 shows the phase lag as a function of frequency.
  • the phase lag shown here is that between the tympanic membrane response and the driving motion of the speaker. This is not to be confused with the phase lag of the static pressure oscillations, which are also in phase with the speaker displacement and are 90 degrees out of phase with the velocity of the speaker and the resulting velocity of air molecules in the trapped volume.
  • the phase lag is the increment in the angular argument of the sine function by which the tympanic membrane response lags the speaker diaphragm driving function. This phase angle corresponds to an actual physical time lag (FIG. 21) of the response of the tympanic membrane vs. the driving oscillation of the diaphragm.
  • FIG.22 shows the tympanic membrane displacement as a percentage of speaker displacement for a 1 cm long trapped volume and frequencies of 10, 100, and 1000 Hz. Compare this to FIG. 13 for the detailed static pressure model. The results in FIG. 22 for 100 Hz are close in valve to those of the static pressure model. The static pressure model indicates that this value is relatively constant to slightly decreasing with increasing speaker displacement. The dynamic model of FIG. 22 again indicates that the value is relatively constant with speaker displacement, but with a slight increase. The tympanic membrane displacement as a percentage of speaker displacement is seen to be highly dependent on frequency. Lower frequencies producing higher percentage displacements and higher frequencies producing lower percentage displacements.
  • FIG. 23 shows the tympanic membrane displacement as a percentage of speaker displacement for a 0.5 cm long trapped volume and frequencies of 10, 100, and 1000 Hz.
  • the smaller trapped volume produces larger percentage displacements of the tympanic membrane.
  • the results in FIG. 23 for 10 to 100 Hz range are close in valve to those of the static pressure model.
  • the static pressure model indicates that this value is relatively constant to slightly decreasing with increasing speaker displacement.
  • the dynamic model of FIG. 23 again indicates that the value is relatively constant with speaker displacement, but with a slight increase.
  • the tympanic membrane displacement as a percentage of speaker displacement is seen to be highly dependent on frequency. Lower frequencies producing higher percentage displacements and higher frequencies producing lower percentage displacements.
  • FIG. 8 for the simple model, FIG. 13 for the detailed static model, and FIG.s 22 and 23 for the dynamic model all show the tympanic membrane displacement as a percentage of the speaker displacement.
  • FIG. 8 shows a high value at low speaker displacements that drops off dramatically with increasing speaker displacement.
  • FIG. 13 shows relatively constant percentage values with a slight down trend for increasing speaker displacement.
  • FIG.s 22 and 23 show relatively constant percentage values with a slight uptrend for increasing speaker displacement. This is an example of a detail that the models do not all consistently predict, and thus it is difficult to draw firm conclusions. It is likely, based on the two more detailed models, FIG. 13 and FIG.s 22 and 23, that this percentage is relatively constant, and for low frequencies the detailed static model and the dynamic model agree quite well on the percentage range. However, one cannot make any conclusion about any up or down trend.
  • the static pressure oscillations in the trapped volume of the ear canal can produce very high SPL especially at lower frequencies, and these static pressure oscillations are distinct from open air sound waves because their pressure oscillations are 90 degrees out of phase with velocity components. Normal, open air sound waves have their pressure oscillations in phase with their velocity components.
  • Audiologists refer to a phenomena known as insertion gain. This is an increase in the SPL of especially lower frequencies when a device, such as a hearing aid is sealed in the ear. Insertion gain is frequently measured by a probe microphone inserted into the sealed volume between the speaker and the tympanic membrane. An audiologist will typically reduce the bass output of a device, such as a hearing aid, in order to compensate for the insertion gain.
  • TVIG Trapped Volume Insertion Gain
  • the TVIG is the difference between the SPL in the sealed ear canal vs. the SPL when the speaker is held in approximately the same position but not sealed with an airtight seal. This is also approximately the same as the difference between the SPL in the sealed ear canal and the SPL that the sound wave would produce in open air.
  • FIG. 24 shows plots of total SPL in the sealed ear canal, including both acoustic waves and static pressure oscillations, vs. frequency.
  • open air SPL (not including any closed volume static pressure effects) is also plotted for the same frequencies and speaker displacements.
  • the open air SPL values represent the acoustic sound waves that coexist in the ear canal with the static pressure waves. Below about 2000-3000 Hz, the oscillating static pressure boosts the overall SPL in the ear canal above the level associated with the acoustic waves. This static pressure boost decreases with increasing frequency.
  • TVIG static pressure gain
  • FIGS. 24a, b, c which span different SPL ranges for the same 10 to 1000 Hz frequency range.
  • the functional form of the TVIG vs. frequency, as shown in FIG. 24 agrees, with what is found experimentally, as discussed below.
  • a probe microphone in the ear canal will measure a smaller TVIG because the motion of the tympanic membrane prevents the buildup of the peak SPL, due to static pressure oscillations, from being achieved in the ear canal.
  • the tympanic membrane absorbs these higher pressure levels via its motion, and thus prevents the probe microphone from recording them.
  • the distinction between TVIG as experienced by the tympanic membrane and TVIG as experienced by a probe microphone is important to understand when comparing to experimental data based on the readings of a probe microphone.
  • FIG.25 shows the same plots as in FIG.
  • the TVIG that would be measured by the probe microphone is about 5 dB lower than the TVIG experienced by the tympanic membrane across the whole frequency range in which a TVIG is found.
  • the TVIG is the difference between the total SPL in the sealed ear canal, including the effect of static pressure oscillations, minus the SPL due only to acoustical waves, which is the same as the open air SPL for which would result from the same speaker motion.
  • the TVIG vs. frequency, as calculated from the model is shown in FIG. 26.
  • FIG. 27a shows the commercially available ear buds used in this study.
  • FIG. 27b shows one of these ear buds sealed in a Zwislocki Coupler for testing.
  • FIG.27c shows one of these ear buds sealed in a human ear (Robert B. herein or RBS) for additional testing.
  • RBS Robot B.
  • tones of various frequency as well as other audio clips were played by the iPhone ® seen in FIG. 27b, through the ear buds.
  • a small probe microphone (Knowles FG), shown in FIG. 28, is placed in the Zwislocki coupler or in the human subject's ear canal to recorded relative sound pressure level SPL as it exists in front of the ear drum.
  • FIG.s 29 shows the output from the probe microphone in the Zwislocki coupler and FIG. 30 shows the output from the probe microphone in the human ear canal during frequency sweeps.
  • the frequency range to look at for comparison to the dynamical modeling of the ear bud sealed in the ear canal is the range below 1000 Hz. Above this frequency range, the validity of the modeling is less sound because the length of the trapped volume is no longer a tiny fraction of the wavelength. Below 1000 Hz, the experimental data in FIGS.29 and 30 shows the same trend as the modeling data in FIGS. 18 and 19.
  • the dynamic model in FIGS. 18 and 19 is showing tympanic membrane displacement in microns, while the experimental data in FIGS. 29 and 30 is plotting a measured quantity referred to as relative SPL.
  • the relative SPL is not absolute SPL, but a log output to indicate changes or differences in sound pressure detected by the probe microphone, in the same units as SPL. Static pressure oscillations detected by this microphone, especially at low frequencies, will produce the same type of response from the microphone as any other sound waves, and thus contribute to relative SPL.
  • This relative SPL is proportional in some way to the pressure driving force in the trapped volume, including both true acoustic sound pressure and oscillating static pressure, the combination of which is responsible for the motion of the tympanic membrane.
  • FIG. 31 illustrates an earbud (SkullcandyTM earbud shown) fitted into a Zwislocki coupler for testing. In Figure 3 la the earbud is inserted into the coupler but not sealed, while in Figure 31b the earbud is in the same position, but is sealed by a rubber gasket.
  • Figure 32a shows SPL measured as a function of frequency with a probe microphone inside the coupler of the test set-up of Figure 31.
  • the blue curve is the SPL measured when the earbud is not sealed in the coupler and the red curve is the SPL, with the same driving signals sent to the earbud, measured when the earbud is in the same position, but is sealed.
  • the green curve is a zero noise calibration of the probe
  • Figure 32c shows the phase shift measured between the sound waves in the unsealed case ( Figure 31a) and in the sealed case ( Figure 31b).
  • FIG. 33 shows the experimentally determined TVIG plotted along with the theoretically calculated values (reproduction of FIG. 26).
  • This general agreement with experiment speaks to the validity of the underlying physical understanding on which the model is based.
  • FIG. 34 shows recently published data on a very similar experiment using insert headphones in a simulated ear canal. Free corresponds to the speaker inserted, but not sealed, in the ear canal. Long corresponds to a shallow sealed speaker insertion, yielding a longer, and therefore larger, trapped volume. Small corresponds to a deeper sealed speaker insertion, yielding a shorter, and therefore smaller, trapped volume.
  • This third party experimental data shows similar magnitudes and trends to our experimental data and our modeling. Additionally, it shows that the influence of oscillating static pressure is more pronounced for smaller trapped volumes than for larger trapped volumes.
  • a 90 degree phase shift indicates a pure oscillating static pressure phenomena, condition approximated below about 30 Hz in the example study.
  • Lower degrees of phase shift indicate the coexistence of oscillating static pressure and normal acoustic sound wave character.
  • Asius Technologies the assignee of the present technology, has developed the test procedure discussed here, as well as a method for analyzing the data that combines the influences of TVIG and phase shift into a parameter or family of parameters, which quantifies the oscillating static pressure characteristics of a given listening device.
  • Red curve is SPL vs. frequency for earbud sealed in coupler.
  • Blue curve is SPL vs. frequency for earbud not sealed in coupler.
  • Green curve is the noise floor.
  • the limits of integration will be from the lowest frequency measured, v 0 up to the place where the phase shift goes to zero Vh.
  • the place the phase shift disappears can be determined for each test or can be set at a fixed, standard value. Since the phase shift is zero above a certain frequency, the upper limit of integration can be a constant frequency that is high enough that the phase shift is never finite above it.
  • the values are cumulative sound intensities over a range of frequencies. These are directly proportional to the power generated over this range of frequencies, the proportionality constant being a characteristic area, which may be the ear canal cross section or the tympanic membrane area. This area, as well as the factor of one half times the reciprocal of the characteristic impedance (pc), need not actually be used in the calculations since it is only the ratios which are of interest and all the units divide out.
  • Oscillating Static pressure detects the triggering of the stapedius (acoustic) reflex when the listener is exposed to a real world sound stimulus such as a piece of popular music.
  • a real world sound stimulus such as a piece of popular music.
  • the stapedius (acoustic) reflex test uses a piece of popular music or some other real world audio program material as the test stimulus.
  • a probe tone is also used to detect the triggering of the stapedius reflex by the stimulus.
  • the real world stimulus (piece of music) has a small band of frequencies (a notch) removed from its spectrum in the vicinity of the frequency of the probe tone. This is to prevent interference of the stimulus with the probe tone.
  • the triggering of the stapedius reflex by the stimulus is detected by an increase in the volume of the probe tone detected by a probe microphone. As in tympanometry, this increase in the detected probe tone volume can be associated with a decrease in the effected trapped volume of the ear canal brought about by the stapedius (acoustic) reflex.
  • the software also performs a test for what is known as "Occlusion Effect.”
  • SPL sound pressure level
  • pulse blood flow
  • IOE the sound pressure level
  • v frequency
  • p s is the sound pressure in Pa due to body noises in the sealed ear
  • 3 ⁇ 4 is the sound pressure in Pa due to voice and natural body noises in the unsealed ear. Note that sound pressures in this equation are expressed on the linear Pa (N/m ) scale rather than the logarithmic SPL (dB) scale.
  • pc is the characteristic impedance.
  • the software package integrates the measurement of oscillating static pressure (Ambrose Number), Stapedius Reflex and Occlusion Effect into a single diagnostic tool for in ear listening devices such as a hearing aid, earbud, and headset. Since oscillating static pressure is a unique, fundamental discovery of the present inventors, the relationship of oscillating static pressure (Ambrose Number) to Stapedius Reflex and Occlusion Effect is a totally new feature of this approach and this software.
  • Figure 51 shows a screen shot of the software package used to evaluate the oscillating static pressure for an earbud tip fitted with a covered vent to reduce the impact of oscillating static pressure.
  • the upper graph shows SPL for the sealed and unsealed conditions, and the graph on the lower right shows the phase difference.
  • the phase difference is about 45 degrees over a broad range indicating a reduction of osciallating static pressure, which would be maximized at a larger phase difference approaching 90 degrees.
  • Figure 52 shows the result of the Ambrose number calculation produced by this software.
  • the software described above can be used with a probe microphone to test the characteristics (oscillating static pressure, stapedius reflex, isolation and occlusion effect) of a particular ear sealing audio device (hearing aid, ear bud, head set) in a particular ear.
  • the results depend upon both the anatomy of the ear and the structure of the device. This is useful, for instance, in fitting and adjusting a hearing aid.
  • the preferred probe includes the following components: (1) an ear seal to produce an acoustic seal in the ear canal, (2) a speaker or sound source which directs sound into the sealed space of the ear canal, (3) a probe microphone measuring sound pressure level (SPL) in the sealed space of the ear canal, and (4) a port between the trapped volume inside the ear canal and the outside air.
  • SPL sound pressure level
  • the port may be opened, closed, or covered with a vent with a flexible membrane covering.
  • this probe can be used to evaluate the acoustical characteristics (e.g., oscillating static pressure, stapedius reflex, isolation, occlusion effect) for a particular ear and it may be used to try out different covered vent options to see which is best for a patient's device (e.g., a hearing aid).
  • the probe of FIG. 53 was constructed by modifying an otoscope.
  • the probe may also be a device with the components described above, but not built on an otosocope.
  • the probe may also contain a port (not shown) connected to a
  • micromanometer in order to measure pressure changes in the ear canal associated with mandibular (jaw) motion.
  • Figure 54 shows a coupler with an inserted earbud.
  • This coupler includes a port which may be open, closed, or covered with various covered vents to perform the measurements necessary to evaluate a particular device for oscillating static pressure.
  • the coupler has a probe microphone built into it, which provides data for analysis by the software.
  • FIG. 35 shows the relative SPL as measured by the probe microphone as a function for frequency, comparing the SkullcandyTM earphones sealed in a Zwislocki coupler to an open-air, desktop speaker.
  • the SkullcandyTM output in the sealed volume of the coupler (red curve) is dramatically higher at low frequencies than the open air speaker (green curve).
  • FIG. 36 shows the TVIG calculated by subtracting the SkullcandyTM output (red curve) from the open air speaker (green speaker), and FIG.
  • the dynamic range of the human cochlea is about 30% narrower than the range of sound pressure levels that can be heard. Louder sounds, above around 80 to 90 dB, are compressed to fit into the dynamic range of the cochlea by a response of the middle ear known as the Stapedius Reflex.
  • the stapedius muscle which is connected to the stapes (stirrup) bone of the middle ear, contracts and thereby tightens the tympanic membrane.
  • the contraction of the stapedius muscle also repositions the ossicles to pull the stirrup back, reducing the amplitude of motions transferred to the oval window of the inner ear.
  • stapedius reflex reduces our sensitivity to sounds at moderate sound pressure levels can be appreciated because of the vocalization-induced stapedius reflex.
  • FIG. 39 shows that one study reported that the stapedius reflex threshold is relatively uniform across a broad range of frequencies and falls in the 70 to 90 dB range for people with normal hearing. [00128] If anything, the stapedius threshold appears to be a little lower at lower frequencies than at higher frequencies, registering as about 75 dB in FIG. 39 at 125 Hz.
  • FIGS. 24 and 25 show modeling results indicating that playing audio, which would yield an SPL of 60 dB in open air, yields an SPL of over 100 dB in a sealed ear canal. This boosted SPL in the trapped volume would certainly trigger the stapedius reflex in an individual with normal hearing.
  • FIG. 32a shows experimental data in which the SPL produced by a SkullcandyTM insert headphone sealed in the ear (red curve) is as high as 75 dB at 100 Hz and below. Absolute SPL values are obtained by subtracting the green background (taken as zero dB) from the graph of interest.
  • the stapedius muscle is like any other muscle in the body in that it will fatigue from overuse. We believe that is a major cause of the listener fatigue reported by some users for insert headphones. In the natural conditions under which humans evolved, the stapedius reflex would likely be triggered somewhat rarely and not for extended periods of time. A person listening to insert headphones, however, may be placing their stapedius muscle in an unnatural state of permanent or near-permanent contraction. This will fatigue the muscle and perhaps other tissues in the ear to which it is connected.
  • FIG. 6 provides a schematic illustration of the fact that a sealed speaker in the ear interacts with the tympanic membrane through two different spring-like volumes of confined air: the trapped volume in the ear canal and the volume of the middle ear.
  • the tympanic membrane rests on a single air spring, the air filled volume of the middle ear. This air spring influences the open ear response of the tympanic membrane and provides a component of the restoring force, which resists its normal displacement.
  • a second air spring is created from the closed volume in the ear canal.
  • the trapped volume in the ear canal may be smaller than the middle ear volume.
  • the stiffness of an air spring is inversely proportional to its volume, and thus the smaller trapped volume in the ear canal can be a stiffer resistance to tympanic membrane motion.
  • This air spring effect contributes to the effectiveness of silicone ear plugs at reducing the perception of noise.
  • the ear plug seals the ear canal creating a trapped volume, air spring, which resists motions of the tympanic membrane.
  • the ear plug reduces what a person hears not only because it blocks sound from entering the ear canal, but also because it creates a trapped volume in the ear canal that helps hold the tympanic membrane still.
  • the oscillating static pressure makes up a large portion of the audio signal at lower frequencies but at higher frequencies, the signal is predominantly acoustical waves. To the extent that the air spring resistance discussed above, damps out acoustical waves, this will disproportionately reduce and distort the high frequency content of audio.
  • the air spring effect of the trapped air in the ear canal will create a back pressure or load on the speaker diaphragm itself. This will require more power to drive the speaker at a given sound output and displacement than in open air. Additionally, this loading may distort the speaker's frequency response and dynamic range. The louder the sound produced by the speaker in a sealed ear condition, the larger the speaker displacement required. This in turn will cause an increasing air-spring resistance to the speaker motion. This will have the effect of resisting higher volume sound production. This effect can be understood quantitatively in terms of the mechanical impedance to sound radiating motion of the speaker as modeled in Beranek.
  • the mechanical impedance of an oscillating surface, radiating sound, including a planar surface sealing off one end of a tube, is proportional to the density of the air in front of the surface.
  • the mechanical impedance as discussed in Beranek refers to the impedance of the motion of the speaker associated with the production of acoustical sound waves. This model does not include any physics to take into account static pressure oscillations. However, it is clear that the static pressure oscillations result in corresponding oscillations in the density of the air in the trapped volume. This leads to oscillations in the mechanical impedance of the speaker, which impact the speaker's coincident production of sound waves.
  • This oscillating impedance of the speaker, associated with lower frequency static pressure oscillations, may have an effect similar to that illustrated in FIG. 40, on the speaker's output of higher frequencies, i.e. a pulsing of the higher frequency wave associated with lower frequency oscillations in speaker impedance.
  • FIG. 40 illustrates a potential distortion that could result from large over- excursions of the tympanic membrane.
  • the springlike resistance of the tympanic membrane to displacement increases with increasing displacement from its resting position (i.e. the zero displacement position of its motion).
  • the lower curve in FIG. 40 shows the tympanic membrane's vibrational response when a high frequency tone is present along with a lower frequency tone, which is producing large over excursions of the tympanic membrane through trapped volume static pressure oscillations.
  • the high frequency waves that occur when the tympanic membrane is near the extremes of its over-excursions produce less of a response (less motion) of the tympanic membrane because the tympanic membrane is stiffened at the extremes of the over excursions.
  • the high frequency waves that occur near the mid-point of the over-excursions produce a larger response from the tympanic membrane because the tympanic membrane is less stiff when it is near is zero of displacement.
  • the upper curve in FIG. 40 shows the resultant displacement of the tympanic membrane due to the higher frequency sound (amplitude expanded relative to the lower curve for clarity). The amplitude of this higher frequency sound beats at a frequency equal to double the frequency of the lower frequency tympanic membrane over-excursions.
  • the invention of the present application is comprised of an in ear or over ear sound device which seals either within the ear canal of the user or over the outer ear of the user.
  • a covered vent is provided in a sidewall portion of the sound device to reduce the trapped volume insertion gain as a result.
  • the vent is provided on an earbud portion of headphones. The vent is in communication with the sound tube of the device. The vent may be adjustable to change the opening of the vent. A plurality of adjustable vents may also be provided in specific embodiments.
  • the vent is provided on a housing of in-ear headphones.
  • the vent is in communication with the sound tube of the device.
  • the vent may be adjustable to change the opening of the vent.
  • a plurality of adjustable vents may also be provided in specific embodiments.
  • the vent is provided on an ear enclosure portion of over ear headphones.
  • the vent is in communication with an interior volume of the ear enclosure of the device.
  • the vent may be adjustable to change the opening of the vent.
  • a plurality of adjustable vents may also be provided in specific embodiments.
  • FIG. 1 is a graph showing the length of a trapped volume as a fraction of a wavelength of sound across a frequency range
  • FIG. 2 is a graph plotting the ratio of the speed of pressure equilibration vs. peak speed of speaker motion across a frequency range
  • FIG. 3 is a reproduction of a prior art test apparatus having a rigid piston oscillating in one end of a rigid tube;
  • FIG. 4 is a graph showing pressure profiles along a one cm tube;
  • FIGS. 5(a-c) are photographs of an Otoscope having an attached earbud
  • FIG. 6 is a schematic of a simplified model for trapped volume in an ear canal
  • FIG. 7 is a graph showing a calculated tympanic membrane displacement vs. speaker displacement
  • FIG. 8 is a graph similar to FIG. 7 except the tympanic membrane
  • FIG. 9 is a graph showing SPL values for speaker motions in open air
  • FIG. 10 is a graph showing peak sound pressures for open air sound and static pressure oscillation amplitude for a sealed ear canal
  • FIG. 11 is a graph similar to FIG. 10 showing a ratio of a sealed volume static pressure to the corresponding open air pressure
  • FIG. 12 is a graph showing tympanic membrane displacement vs. speaker displacement
  • FIG. 13 is a graph similar to FIG. 12 showing tympanic membrane displacement as a percentage of speaker displacement
  • FIG. 14 is a graph similar to FIG. 12 showing tympanic membrane displacement as a percentage of overall displacement
  • FIG. 15 is a graph showing peak sound pressure or open air and static pressure for the sealed ear canal volume as a percentage of atmospheric pressure
  • FIG. 16 is a graph showing maximum static pressure generated in a trapped volume of an ear canal
  • FIG. 17 is a graph showing data similar to that of FIGS. 15 and 16;
  • FIG. 18 is a graph showing tympanic membrane displacement vs. frequency for a range of speaker displacements for a one cm trapped volume
  • FIG. 19 is a graph showing tympanic membrane displacement vs. frequency for a range of speaker displacements for a 0.5 cm trapped volume
  • FIG. 20 is a graph showing a phase lag of the tympanic membrane response to a speaker motion
  • FIG. 21 is graph showing a time lag equivalent of the data of FIG. 20;
  • FIG. 22 is a graph showing tympanic membrane displacement as a percentage of speaker displacement for a one cm trapped volume
  • FIG. 23 is a graph showing tympanic membrane displacement as a percentage of speaker displacement for a 0.5 cm trapped volume
  • FIGS. 24(a-c) are graphs showing open air and sealed ear SPL data along a range of frequencies for 1, 10 and 100 micron speaker displacements;
  • FIGS. 25(a-c) are graphs showing open air and sealed ear SPL data along a range of frequencies for 1, 10 and 100 micron speaker displacements as measured by a probe of the present invention
  • FIG. 26 is graphs showing TVIG vs. frequency
  • FIGS. 27(a-c) are a series of images of a commercial brand earbud sold under the tradename SkullcandyTM used is a test apparatus and positioned in a user's ear;
  • FIG. 28 is an image showing a probe microphone sold by Knowles
  • FIG. 29 is a graph showing data results of the set-up illustrated in FIG. 27(b);
  • FIG. 30 is a graph showing data results of the set-up illustrated in FIG. 27(b) vs. the set up in FIG. 27(c);
  • FIGS. 3 l(a, b) are images of a ear-tip in a Zwislocki coupler, unsealed and sealed, respectively;
  • FIGS. 32(a-c) are graphs showing data results of the set-ups illustrated in FIGS. 31a,b;
  • FIG. 33 is a graph comparing the experimental data to the model for determining insertion gain
  • FIG. 34 is a graph reproduced from "Modeling of External Ear Acoustics for Insert Headphone Usage” J. Audio Eng. Soc, Vol. 58, No. 4, 2010, pp. 269-281;
  • FIG. 35 is a graph showing relative SPL for a "Conga Drum” loop measured by the apparatus of FIG. 31b and a open air desktop speaker;
  • FIG. 36 is a graph showing a difference between the two apparatus charted in FIG. 35; [001871
  • FIG. 37 is a graph showing model vs. experimental data for insertion gain at a range of frequencies;
  • FIG. 38 is graph comparing relative phase in degrees of sealed and non-sealed couplings
  • FIG. 39 is graph reproduced from "Stapedius Reflex Test, Brainstem
  • FIG. 40 is a graph illustrating a potential distortion from large over-excursions of the tympanic membrane
  • FIGS. 41(a,b) are images showing a typical commercial form of an earbud construction
  • FIGS. 42(a-h) are images of earbud tips showing different embodiments made in accordance with the invention of the present application.
  • FIGS. 43(a-f) are images of earbud tips showing different embodiments made in accordance with the invention of the present application.
  • FIGS. 44(a-e) are images of earbud tips showing different embodiments made in accordance with the invention of the present application;
  • FIGS. 45(a,b) are images of embodiments of over-ear headphones made in accordance with the invention of the present application.
  • FIGS. 46(a-d) are images of embodiments of a balanced armature transducer made in accordance with the invention of the present application.
  • FIGS. 47(a,b) are images showing a hearing aid tip as it might be modified in accordance with the invention of the present application;
  • FIGS. 48(a-c) are images illustrating the modification of a earbud in accordance with an embodiment of the present invention.
  • FIGS. 49(a,b) are graphs showing data comparing the SPL of the device of FIG. 48 to that of a similar non-vented earbud tip;
  • FIG. 50a is an image reproduced from "A Guide to Tympanometry for Hearing Screening" by T. K. Mikolai, J. Duffey, D. Adlin, MAICO DIAGNOSTICS, 7625 Golden Triangle Drive, Eden Prairie, MN;
  • FIG. 50b is an image showing modification of the device shown in FIG. 50a;
  • FIG. 51 is a screen shot showing a graph from a software test on oscillating static pressure
  • FIG. 52 is a screen shot from software showing the "Ambrose number" calculated
  • FIGS. 53(a,b) are images illustrating an embodiment of an in ear probe design
  • FIG. 54 is an image of a coupler with an inserted earbud
  • FIG. 55 is an image illustrating an embodiment of an earbud and headphone tip made in accordance with the present invention.
  • FIGS. 56(a-d) are images illustrating embodiments of a headphone tip made in accordance with the present invention.
  • FIGS. 57(a,b) are images illustrating the modification of a headphone tip in accordance with an embodiment of the present invention.
  • TVIG trapped volume insertion gain
  • Some in-ear listening devices such as hearing aids and in-ear monitors for musicians require an acoustic seal in the ear to prevent feedback from nearby microphones.
  • the inventive theme that runs through many of the embodiments presented below, is that a compliant surface added to some part of the enclosure creating the trapped volume in the ear canal acts to partially or fully transform oscillating static pressures, which are high in amplitude (high SPL) and are 90 degrees out of phase with the velocity component of the sound waves, into normal sound waves which are lesser in amplitude and are more in phase with their velocity components. This then reduces trapped volume insertion gain (TVIG) and prevents the stapedius reflex.
  • high SPL high in amplitude
  • TVIG trapped volume insertion gain
  • the ADEL bubble is like a pneumatic shock absorber that deforms or flexes to relieve some of the static pressure build up, produced by the motion of the speaker, which is responsible for static pressure oscillations and tympanic membrane over excursions.
  • the light and flexible bubble seal can retract slightly to negate some of the volume change and reduce static pressure build up.
  • a slightly under-inflated bag-like structure made of a non-extensible material such as expanded polytetrafluoroethylene (ePTFE), is ideal for performing this function.
  • the inflatable ear seal as a means for reducing trapped volume insertion gain, and for preventing insert headphones or hearing aids from triggering the stapedius reflex.
  • the compliance of the inflatable bubble seal acts to partially or fully transform oscillating static pressures, which are high in amplitude (high SPL) and are 90 degrees out of phase with the velocity component of the sound waves, into normal sound waves which are lesser in amplitude and are more in phase with their velocity components.
  • the donut bubble in which there is an open sound tube piercing the middle of the inflatable seal providing a direct connection between the speaker diaphragm and the trapped volume in the ear canal; and the driven bubble, in which the inflatable member completely encloses the end of the sound tube.
  • the driven bubble the speaker impinges upon a closed volume comprising the interior of the driven bubble, and this volume is separated by the bubble wall from the volume sealed in the ear canal.
  • both the donut bubble and driven bubble versions of the inflatable ADEL ear seal transduce sound energy directly into the ear canal wall.
  • Direct transduction of sound through the ear canal walls and through tissue and bone directly to the cochea provides a path for sound energy that does not involve over-excursions of the tympanic membrane, and is therefore less likely to stimulate the stapedius reflex.
  • Some in-ear hearing devices require an acoustic seal isolating the ear canal from the outside air. Such devices are subject to the problems of static pressure oscillations, tympanic membrane over-excursions, and triggering of the stapedius reflex, as discussed above. Simply putting a vent or hole in the ear seal to prevent static pressure build up is not, in some cases a viable alternative because the device will feedback.
  • a vent in an ear seal that is covered by a thin flexible membrane. This covered vent allows the relief of static pressure build up (including both positive and negative pressures), through deformation of the thin flexible membrane.
  • This deformation of the covering of the vent may include expansion or contraction; bowing out or bowing in; and performing these motions as vibrations at acoustical frequencies.
  • the function of the covered vents may be described as the radiating of acoustical energy out of the sealed volume of the ear canal. Either description leads to the same function for the covered vents: to reduce pressure and SPL in the ear canal so as to reduce over excursions of the tympanic membrane and to prevent to stapedius reflex.
  • a wide range of vent geometries, numbers of vents, and the like are possible on a wide range of ear sealing devices. Vents filled with bubbles containing air or some other compliant filling can perform the same function as vents covered with thin flexible membranes.
  • FIG. 41a shows how the insert headphone tip slips over the snout of the earphone body.
  • FIG. 41b shows the structure of a typical insert headphone tip.
  • a hollow, sound tube connects the sound source in the earphone body, through the ear tip, into the ear canal.
  • the acoustic seal is provided by a "mushroom cap” structure which flares out around the end of the sound tube facing into the ear canal.
  • FIG. 42 shows one set of embodiments of the present invention.
  • FIG.42a shows an embodiment with a single hole in the sound tube. This hole is covered by a flexible membrane material.
  • FIG.42b shows an embodiment in which a number of such covered vents are distributed around the circumference of the sound tube.
  • Embodiments of this invention, with respect to the number, geometry and placement of covered vents, are not limited by FIG. 42. For instance, multiple covered vents may be distributed along the length of the sound tube, instead of, or in addition to around it circumference. Covered vents need not be circular holes, as in FIG. 42.
  • the flexible membrane material covering the vents may be a polymeric membrane, or another membrane material including a lightweight metal foil or a metal covered polymer membrane.
  • the flexible membrane covering the vents may be any one of the materials or classes of materials from which ADEL bubble can be produced, and which are listed in our previous patent filings.
  • the covered vents in the sound tube are shown to be under the mushroom cap of the insert ear tip. This is not a requirement of the invention. These vents may be anywhere along the sound tube, however, placement under the mushroom cap is potentially desirable both esthetically and as a protection for the membrane coverings of the vents.
  • FIG. 42c shows an embodiment in which the covered vents, are not individually covered, as in FIGS.42a and b, but rather are collectively covered by a snug fitting sleeve of the flexible membrane material, which surrounds a section of the outside of the sound tube.
  • FIGS.42d-h show embodiments in which the insert ear-tip with covered vents is molded as a single piece of polymeric material.
  • This single molded piece includes the vent holes and the vent covers. This is accomplished by molding holes into the sound tube that do not penetrate all the way through the sound tube wall, leaving a very thin membrane of the same material that composes the sound tube covering the hole.
  • This membrane of molded material is thinner than the wall thickness of the sound tube, and is preferably thinner than 100 micrometers, and is most preferably thinner than 40 micrometers. The remaining membrane of molded material covering the hole may be flush with the inside of the sound tube.
  • FIG. 42d shows an embodiment with a single hole in the sound tube, which thins the wall of the sound tube but does not penetrate all the way through the sound tube.
  • FIG.42e shows an embodiment with a number of such holes covered by films of the same molded material as the sound tube.
  • the membrane of molded material covering the hole(s) in the sound tube may be smooth, as in FIGS.42d and e, or it may be textured or embossed as in FIGS.42f and g.
  • the texture may be concentric circles (FIG. 42f), a spiral, a dimpled or wrinkled pattern (FIG. 42g), or some other pattern or texture.
  • the thin membrane(s) of molded material may be a dome shaped and they may be convex (sticking out from the sound tube) or concave, sticking down toward the center of the sound tube.
  • All insert headphone ear tips with covered vents or other embodiments of this invention are designed with an elastic boot fitting that allows them to fit over the snout of virtually any commercially available insert headphone, as shown in FIG. 41a.
  • FIG. 43 shows an embodiment in which the pressure relieving function of the covered vents is adjustable.
  • a snug fitting sleeve of a more rigid material covers the vents in the sound tube.
  • the vents themselves are still covered by the flexible membrane material, either individually or via another sleeve of this flexible membrane material, which is beneath the sleeve of rigid material.
  • There are holes in the outer, rigid sleeve which correspond in size and arrangement to the underlying covered vents in the sound tube.
  • the entire outer, rigid sleeve can be rotated around the sound tube to either align (FIG. 43a), partially misalign (FIG.43b) or completely misalign (FIG. 43c) with the underlying covered vents in the sound tube.
  • FIG. 43a shows another embodiment in which the holes in the outer sleeve are not open, but are themselves covered with a flexible material.
  • the rigid, outer sleeve in FIG. 43 may be fitted with a manually operated handle or switch (not shown) that allows the user to adjust the alignment of holes and covered vents.
  • the rigid outer sleeve may also fit into a coupling on the body of the headphone (not shown) when the ear tip is attached, as in FIG. 41a, and then the alignment of holes and covered vents may be controlled by a manual or power driven motion transmitted from the headphone body.
  • the sleeve of flexible membrane material (FIG. 42c) and the rigid, outer sleeve with holes (FIG. 43) have been shown on the outside of the sound tube. They can also be placed on the inside of the sound tube and perform the same function. For instance, the inside of the sound tube may be covered with a cylindrical lining of the flexible membrane material in the region of the vents. Additionally, a rigid, cylindrical, inner sleeve with holes in it can be inserted into the sound tube rotation of this inner cylinder to align or misalign its holes with the covered vents in the sound tube can perform the same pressure relief adjustment as the device shown in FIG. 43.
  • FIG. 43 e shows an embodiment similar to FIGS. 43a-c, but with the difference that the sleeve of rigid material slides along the sound tube, rather than rotates, in order to align or misalign holes with covered vents.
  • the sliding, rather than rotation sleeve can be used either on the outside of the sound tube as shown in FIG. 43 e, or on the inside of the sound tube (not shown).
  • FIG. 43f shows an embodiment in the holes in a rotating sleeve of rigid, or semi-rigid, material have different sizes. The use of different sized holes may be used, rather than alignment and misalignment as in FIGS. 43a-c, as a means to adjust the activity of the covered vents in the sound tube.
  • the sleeve with the different sized holes may be outside the sound tube, as shown in FIG. 43 f, or it may be inside the sound tube.
  • the different sized holes may be changed by rotation of the sleeve, as shown in FIG. 43 f, or be sliding analogous to FIG. 43e.
  • All of the embodiments of FIG. 43 could also be constructed with the covered vents located in the rotating or sliding rigid (or semi-rigid) sleeve (placed inside or outside the sound tube). In these embodiments, there would be holes in the sound tube, which are either aligned or misaligned with the covered vents in the moving sleeve.
  • the function of relieving static pressure build up in the sealed volume comprising the ear canal and the sound tube can also be accomplished, as shown in FIG. 44, by placing gas filled bubbles, or bubbles filled with some other suitably compliant fluid (such as a liquid or gel), in the wall of the sound tube or within the interior of the sound tube.
  • gas filled bubbles or bubbles filled with some other suitably compliant fluid (such as a liquid or gel)
  • FIG. 44a shows an embodiment with a single bubble in the wall of the sound tube.
  • the surface of the bubble is made of the same type of flexible membrane material as the vent covers discussed in the previous section.
  • the interior of the bubble may contain a gas, which would commonly be air, but could be another gas such as helium, nitrogen, oxygen, argon, or the like.
  • the interior of the bubble may also contain another fluid or compliant material such as a liquid or a gel.
  • the bubble in this embodiment, spans the wall of the sound tube, with part of the bubble surface exposed to the interior space of the sound tube and part of the bubble surface exposed to the outside of the sound tube.
  • FIG. 44b shows an embodiment in which multiple bubbles, of the type in FIG. 44a, are distributed in the sound tube wall.
  • FIG. 44c shows an embodiment in which a bubble of the same type is enclosed completely within the sound tube.
  • Other versions of this embodiment may have multiple bubbles enclosed completely within the sound tube.
  • FIG. 44d has a bubble or bubbles, imbedded in the inner wall of the sound tube. These bubbles must have some of their flexible membrane outer surface exposed to the interior of the sound tube. The rest of the bubbles' surface is encased in the wall of the sound tube, and the bubble surface does not contact the space outside the sound tube.
  • the bubbles may be fully inflated or they may be under-inflated so that the membrane material enclosing them is loose. This loose bubble covering may be wrinkled.
  • the static pressure relieving function of the bubble(s) may be adjustable via an adjustment of pressure in the bubble through a pressurization tube, as shown in FIG. 44e.
  • Embodiments with multiple bubbles may have multiple pressurization tubes, and may have a pressurization manifold that feeds multiple variable pressurization bubbles.
  • the pressure relieving function of the bubbles may also be adjustable by partially covering their surfaces where they contact the interior of the sound tube or the space outside the sound tube.
  • One embodiment that achieves this uses a rigid or semi-rigid, rotating sleeve with holes in it (as in FIG. 43), but now applied over bubble filled openings in the sound tube. Other means of covering part or all of the bubbles' surfaces are equally valid embodiments of this invention.
  • the covered vent or vents may also be placed in the hard plastic or metal case of the earbud which forms part of the front volume of the speaker and to which the rubber mushroom ear-tip attaches.
  • FIG. 55 shows such a covered vent on an earbud case.
  • the covered vents on the earbud case may be covered with a sleeve with holes in it in order to allow the user to adjust the influence of the covered vents.
  • the holes in the sleeve may be any shaping, including circular, oval, rectangular, tear drop, etc. All of the schemes for arrangements of covered vents and a sleeve to adjust their effect, which were shown for use around the sound tube, may also be applied to the rigid case/housing of the earbud, where that case covers the front volume of the speaker.
  • the covered vents on the front volume of the earbud casing may also be placed on the front of the casing as shown in FIGS. 56(a-d), rather than on the side of the earbud casing, as shown in FIG. 55.
  • One or more covered vents may be placed on the front of the earbud casing around the sound tube.
  • These covered vents may also be covered by an annular disk of more rigid material having holes therein. This annular disc may be rotated to expose different amounts of covered vent surface are with the holes of the annual disc. This allows the user to adjust the amount of oscillating static pressure and thus the acoustical characteristics of the earbud.
  • the covered vents themselves and the holes in the annual disk may be any convenient shape including, but not limited to, circular, oval, rectangular, tear drop shaped, etc.
  • the covered vents used in the inventions disclosed in this application may be constructed by placing a flexible membrane material, such as expanded
  • ePTFE polytetrafluoroethylene
  • the short cylinder, hoop, or islet may be covered by a rigid surface, parallel to the compliant membrane, and this rigid surface may contain one or more ports (holes). These ports allow airflow to facilitate the movement of the compliant membrane, while adjusting the acoustical performance of the device.
  • over-ear headphones fit snuggly to the sides of the head, they can create a trapped volume that is continuous with the ear canal. Sealed, or partially sealed, over-ear headphones therefore can also subject the tympanic membrane to large amplitude static pressure oscillations resulting in over-excursions of the tympanic membrane. The effect is not as pronounced as in inert headphones due to the much larger size of the trapped volume. However, listener comfort and safety, as well as sound quality can still be enhanced by adding static pressure relieving elements, as shown in FIG. 45.
  • FIG. 45a shows over ear headphones with a covered vent in the wall of the ear enclosure.
  • This covered vent is a hole connecting the interior of the enclosure with an outside that is covered by a flexible membrane material.
  • the membrane material is from the same group as listed previously for covered vents in insert headphones.
  • These vents may be covered or partially covered by an adjustable cover of greater rigidity than the flexible membrane, analogous to the scheme of FIG. 43, for the purpose of allowing adjustment to the pressure relieving properties.
  • These bubbles or vents may be in direct contact with the outside air or may face into a cavity inside the outer housing (can) of the headphone as long as this space is, in-turn vented to the outside atmosphere.
  • FIG. 45b shows over ear headphones with a bubble in the wall of the ear enclosure.
  • This bubble may have free surfaces in contact with the interior of the enclosure and with the outside (either directly or through contact with another vented space), it may be embedded in the enclosure wall and thus only be in contact with the interior space, or it may be completely contained in the ear-enclosure of the headphone.
  • the pressure relieving function of the bubbles may be adjustable by partially covering their surfaces where they contact the interior of ear-enclosure or the space outside the enclosure.
  • the bubble(s) in the headphone of FIG.45b may be fully inflated or they may be under-inflated so that the membrane material enclosing them is loose. This loose bubble covering may be wrinkled.
  • the static pressure relieving function of the bubble(s) may be adjustable via an adjustment of pressure in the bubble through a pressurization tube (not shown).
  • Embodiments with multiple bubbles may have multiple pressurization tubes, and may have a pressurization manifold that feeds multiple variable pressurization bubbles.
  • a toroidal or donut shaped bubble completely surrounds the inside of the earphone on the inside of the foam enclosure which surrounds the ear.
  • a toroidal or donut shaped bubble completely surrounds the inside of the earphone taking the place and performing the function of the foam enclosure that surrounds the ear.
  • FIG. 46a the open space on the front side of the diaphragm, but within the outer housing or case of the balanced armature transducer is known as the Front Volume.
  • the Front Volume is part of the trapped air volume which includes the sealed part of the ear canal. Placing a covered vent, as shown in FIG.
  • This covered vent can reduce oscillating static pressure, reduce trapped volume insertion gain, and prevent the triggering of the stapedius reflex.
  • closed bubbles in the outer housing of the front volume or fully or partially contained in the front volume may also be used to achieve these benefits.
  • FIG. 46c shows a balanced armature transducer with a vent covered with a flexible membrane in its back volume. This location of the covered vent does not reduce static pressure in the ear canal, does not reduce trapped volume insertion gain, and does not prevent the triggering of the stapedius reflex.
  • the device shown in FIG. 46c is a separate invention that allows the transducer to operate acoustically and mechanically as if its back volume is much larger than the actual space it occupies. This allows improved speaker performance and eliminates that need for a tuned vent or port in the back volume. Such a vent or port may be disadvantages because it can cause feedback.
  • FIG. 46d shows an embodiment in which there are vents covered with flexible membranes in both the front volume and the back volume of the balanced armature transducer. This embodiment allows the advantages of increased effective back volume as in FIG.46c, while also reducing static pressure in the trapped volume of the ear canal, reducing trapped volume insertion gain, and mitigating the stapedius reflex.
  • Hearing aids that seal in the user's ear produce the same undesirable trapped volume effects (high pressures and over-excursions of the tympanic membrane) inset headphones.
  • FIG. 47a shows a commercial, receiver in canal (RIC) type hearing aid with an open-ear architecture.
  • this device includes open-hole vents in the ear tip.
  • This type of device is not suitable for people with severe hearing loss because feedback caused when large amplifications are used.
  • This device can be modified according to this invention by placing thin flexible membranes over the vent holes in the ear tip. Alternatively gas filled bubbles could be placed in these holes, or these holes could be closed and a sealed vent or bubble could be placed in the diaphragm of the receiver in the ear tip.
  • RIC devices like this generally use balanced armature transducers, and thus this device could also be made to practice our invention by putting a covered vent or vents or a bubble or bubbles in the front volume.
  • a hearing aid with covered vents in the ear seal as shown in FIG. 47b, (or another embodiment of the present invention) will have greatly reduced insertion gain (which is related to the trapped volume insertion gain measured in this disclosure), thus making at least one of the adjustments that an audiologist performs when fitting a hearing aid to a patient, un-necessary.
  • the present invention will aid the development of hearing aids which do not need professional fitting, but still perform well. This development will greatly decrease the cost and increase the availability of hearing aids.
  • FIG.48 a shows a SkullcandyTM ear tip on a wooden mandrel with its mushroom cap turned up. A 3 mm diameter hole has been punched into its sound tube. On the upper left, a sleeve of expanded polytetrafluoroethylene (ePTFE), a light weight, flexible membrane material, is waiting to be used.
  • FIG. 48b shows the SkullcandyTM ear tip with the ePTFE sleeve covering the hole in the sound tube, thereby creating a covered vent of the type disclosed in this filing.
  • FIG. 48c shows the same modified ear tip with the mushroom cap turned down (its normal position). The ePTFE covered sealed vent is visible from the inside of the sound tube.
  • ePTFE expanded polytetrafluoroethylene
  • FIG.49 shows the results of testing on this inventive ear tip with a covered vent.
  • FIG. 49a shows the relative SPL vs frequency for the inventive ear tip as compared to the same type of ear tip without the covered vent, both sealed in a Zwislocki coupler. There is a clearly a marked reduction in relative SPL for frequencies below 3000 Hz, showing the inventive ear tip reduces static pressure oscillation in the ear canal, and therefore reduces SPL and over-excursions of the tympanic membrane.
  • FIG. 49b shows similar experimental data comparing the inventive device sealed in a human ear vs. the unmodified ear tip.
  • the ear tip with covered vents is shown to reduce SPL, indicating a reduction in pressure in the ear canal and therefore and reduction in over-excursions of the tympanic membrane. Reductions of 5 to 20 dB were brought about by the inclusion of a single covered vent in the ear tip. This reduction in the trapped volume insertion gain has strong likelihood of preventing the stapedius reflex under normal listening conditions, and thereby preventing audio fatigue and potentially preventing long term hearing damage.
  • the inflatable ear seal and the vented ear tips work better because they have an automatic sensing and response mechanism built in that allows them to respond to the static pressure oscillations while they are occurring and simultaneously allow the acoustical content to pass through.
  • the inventive devices thereby convert oscillating static pressure waves, or at least enough of this pressure to improve the listening experience, back into normal acoustical sound energy in which the pressure oscillation and the velocity component are in phase.
  • devices for sensing higher pressure levels and high SPL levels in the trapped volume of the ear canal when a sound producing device is sealed in the ear canal are disclosed. These devices detect high pressures or high SPL though the use of a pressure sensitive material.
  • This pressure sensing material undergoes a change when exposed to a given level of static pressure and/or SPL, and this change results in an indication of exposure to said pressure or SPL.
  • Examples of useful sensing materials for this application are piezoelectric materials that produce an electrical voltage when subjected to a pressure.
  • a number of polymer (plastic) materials, suitable for incorporation into ear buds, insert eartips, headphones, and the like are piezoelectric, notably polyvinylidenefluoride (PVDF).
  • PVDF polyvinylidenefluoride
  • a piezoelectric material incorporated into ear-tips may produce an electrical signal warning of high pressure or SPL which is picked up by connections on the headphone housing and transferred to a readout on the headset or on the electronic audio device.
  • the electrical signal generated by high pressure or high SPL may also lead to a secondary effect, such as a change in color of the material, which warns the user.
  • a sensing material is a polymer or other material containing microscopic or nanoscopic vesicles, micelles, or other small containment vehicles (particles), that contain or sequester a dye or other chemical agent.
  • containment vehicles vesicles, micelles, or the like
  • SPL surface tension
  • These pressure or SPL sensitive ear tips, headphones, RIC hearing aid ear pieces, and the like may be designed for one time use, i.e. they turn color when exposed to dangerous pressure or SPL and they do not change back when the pressure or SPL is removed.
  • these pressure or SPL sensitive ear tips, headphones, RIC hearing aid ear pieces, and the like may produce a continuous readout of pressure level. This may be a two state readout indicating a dangerous level has been exceeded or not, and once the pressure or SPL is removed or lowered, the device may change back from its excited or warning state to its normal state.
  • the device may provide more detailed, ongoing indication of pressure or SPL level, either through an electronic readout or by some other change like progressing through a spectrum of colors.
  • FIG. 50a shows the general scheme of the insert ear-piece used for tympanometry.
  • Three different tubes piece the ear seal to provide sound from a speaker, access for an external microphone, and pressure regulation via an external pump and manometer. This device, as shown, is not suitable for testing to see whether commercial insert headphones, ear buds, or hearing aids trigger the stapedius reflex during normal use.
  • FIG. 50b In order to do a realistic test of real in-ear devices, the schematic is modified, as shown in FIG. 50b.
  • the ear seal and the speaker of FIG. 50a are replaced by an insert headphone or hearing aid to be tested (such as the SkullcandyTM used above). This allows removal of the long tube to the speaker in FIG. 50a.
  • the external microphone and tube leading to it are replaced by an insert probe microphone of the type shown in FIG. 28. This microphone can be inserted in the ear canal during testing, and its wire connection can be threaded through the ear seal without breaking the seal.
  • the source of pressure in FIG.50a is replaced by the static pressure induced in the sealed ear canal by the speaker of the device to be tested.
  • the elimination of all the tubes running through the ear seal to external devices dramatically decreases the size of the trapped volume and allows realistic testing of the influence of effects such as oscillating static pressure and trapped volume insertion gain on the triggering of the stapedius reflex.
  • the procedure to do a reflex tympanometry test on real headphones or hearing aids can be the same or similar as the usual diagnostic procedure.
  • a probe tone is used to measure the impedance of the tympanic membrane to detect stiffening due to the stapedius reflex, while another louder tone, at a different frequency is used to induce the stapedius reflex.
  • a test with the device of FIG. 50b to see whether listening to music or other audio material with the device to be tested (insert headphones, hearing aids, etc.) induces the stapedius reflex. This is done by taking a piece of audio program material (music, etc.) and using a notch filter to remove a specific band of frequencies, around the frequency of the probe tone to be used for tympanometry, from this audio program. Then the tympanometry test is performed using the audio program material played at different volumes.
  • the test tone frequency which is not interfered with by the audio program, is simultaneously used to measure the impedance of the tympanic membrane to detect the onset of the stapedius reflex, as the SPL from the audio material is increased.
  • the invention of FIG. 50b can be used to test for the threshold of the stapedius reflex when fitting hearing devices and hearing aids to patients. It can be performed using the actual device being fitted (rather than the standard tympanometry earpiece) because this allows the real trapped volume effects including TVIG and triggering of the stapedius reflex to be tested for real listening conditions with the actual device.
  • the invention of FIG. 50b may be used to properly select and proscribe an ear-tip with sealed vents, an ADEL bubble ear tip, or any of the other embodiments disclosed in this application, to prevent TVIG and the stapedius reflex.

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  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Headphones And Earphones (AREA)

Abstract

L'invention concerne un dispositif, un système et un procédé pour oreille qui, en utilisant au moins une ouverture aérée, aident à protéger contre un état potentiellement dommageable de perte temporaire et même permanente de l'audition résultant de la pression statique oscillante dans un conduit auditif hermétique. Des modes de réalisation comprennent un dispositif d'aération pour des écouteurs boutons, des casques d'audition, des aides auditives, des transducteurs à induit équilibré et similaire.
EP11838808.1A 2010-11-03 2011-11-03 Dispositif, système et procédé audio Withdrawn EP2636225A2 (fr)

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US40972410P 2010-11-03 2010-11-03
PCT/US2011/059137 WO2012061594A2 (fr) 2010-11-03 2011-11-03 Dispositif, système et procédé audio

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US9363594B2 (en) 2013-12-13 2016-06-07 Apple Inc. Earbud with membrane based acoustic mass loading
EP2928203A1 (fr) * 2014-04-03 2015-10-07 Oticon A/s Dispositif d'aide auditive
GB201714956D0 (en) * 2017-09-18 2017-11-01 Sonova Ag Hearing device with adjustable venting
EP3637789B1 (fr) * 2018-12-04 2023-04-05 Sonova AG Appareil auditif à chambres connectées acoustiquement et son procédé de fonctionnement

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US7130437B2 (en) * 2000-06-29 2006-10-31 Beltone Electronics Corporation Compressible hearing aid
GB0806538D0 (en) * 2008-04-10 2008-05-14 Sensorcom Ltd Earpiece member
US8452392B2 (en) * 2008-07-31 2013-05-28 Acclarent, Inc. Systems and methods for anesthetizing ear tissue

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