WO2001006916A1 - Reduction active de bruit pour audiometrie - Google Patents

Reduction active de bruit pour audiometrie Download PDF

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Publication number
WO2001006916A1
WO2001006916A1 PCT/US1999/016293 US9916293W WO0106916A1 WO 2001006916 A1 WO2001006916 A1 WO 2001006916A1 US 9916293 W US9916293 W US 9916293W WO 0106916 A1 WO0106916 A1 WO 0106916A1
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Prior art keywords
control
noise
audiometry
test
test stimulus
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PCT/US1999/016293
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English (en)
Inventor
William R. Saunders
Michael A. Vaudrey
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Saunders William R
Vaudrey Michael A
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Publication date
Application filed by Saunders William R, Vaudrey Michael A filed Critical Saunders William R
Priority to AU51119/99A priority Critical patent/AU5111999A/en
Priority to PCT/US1999/016293 priority patent/WO2001006916A1/fr
Publication of WO2001006916A1 publication Critical patent/WO2001006916A1/fr

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/12—Audiometering
    • A61B5/121—Audiometering evaluating hearing capacity

Definitions

  • ANR active noise reduction
  • This invention relates to the application of any one of a variety of ANR techniques to audiometry testing and to corresponding embodiments of audiometry testing headphones. Specifically, the reduction or cancellation of ambient noise of any spectral content existing in and/or around the vicinity of an audiometric testing facility is the main object of the invention. Audiometry testing stimuli are compensated in appropriate ways, after the application of the ANR method, resulting in accurate testing results that conform to standard calibration procedures.
  • This invention includes the field of electronic equipment used for audiometry testing as well as the field of electronic devices used for personal ANR implementations.
  • Audiometric testing requires very low ambient noise levels in order to determine a subject's hearing threshold level.
  • Ambient noise may refer to the noise heard by the user under the audiometric test headphones or to the noise in the immediate area surrounding the test subject. The specific meaning will be clear in the context of the subsequent discussion.
  • two methods have been used to achieve low ambient noise environments where test subjects can be accurately tested. Artificially quiet environments have been created by installing various sizes of soundproof testing booths (chambers or rooms) in locations that are otherwise too noisy.
  • An alternative to this expensive option has been to add more passive attenuation materials to existing headphones, thus enclosing the ear in a chamber called a circumaural headphone architecture (such as the Audiocup).
  • ANR techniques to reduce the acoustic noise perceived by a human listener has become quite popular in the last ten years.
  • none of the headsets have been designed to be integral components in hearing evaluation equipment or for the purpose of improving the quality of audiograms generated in situ.
  • the instant innovations significantly advance the state-of-the-art for ANR headphones, providing a completely new design process and fabrication than previously defined by prior inventors.
  • Yet another object of this invention is to provide for audiometric testing in high ambient noise conditions using active noise cancellation techniques and, .
  • Figure 1 illustrates the general inclusion of active noise reduction in audiometry in a manner such that each of the critical components stand alone.
  • Figure 2a shows a conventional audiometry testing system in block diagram form.
  • Figure 2b shows the same conventional system with a quantitative measure of the sound reaching the test subject's eardrum.
  • Figure 3 illustrates a generalized relationship between the actuator, sensor and user for an active noise control application where the exact location of the microphone is a function of both the distance from the speaker and the distance from the user.
  • Figure 4a shows a headphone implementation for the active control components used in audiometry where the actuator delivers both the test stimulus and the control force.
  • Figure 4b illustrates one possible embodiment where separate actuators are used , for test stimulus delivery and noise control.
  • Figure 5 shows one possible position for the error sensor required for active noise control in a standard audiometry test headset such that the inclusion of the sensor has no physical affect on the calibration procedure or normal fit of the cushion to the test subjects pinna.
  • Figure 6 illustrates another possible implementation where two actuators can be used, one for test stimulus delivery and one for control force delivery.
  • the test stimulus is delivered by an insert earphone and the control force is included in a circumaural ANC headset device designed to minimized ambient noise for the purpose of performing audiometry testing.
  • Figure 7 shows one possible actuator, sensor, and passive noise control configuration that does not meet the current standards for audiometry due to the cicumaural cushion, but may provide excellent performance if the proper calibration procedure is specified.
  • Figure 8 is a general feedback control block diagram designed for disturbance rejection.
  • Figure 9 is a more specific illustration of how analog feedback control can be used to reject ambient noise in an audiometer system.
  • Figure 10 is a similar embodiment to that of Figure 9, but implements the feedback controller using digital components as well as analog components
  • Figure 11 illustrates feedforward noise control for use in rejecting ambient disturbances in audiometry while also offering two possible options for delivering the audiometer test stimulus.
  • Figure 12 illustrates combined feedback and feedforward active noise control for use in rejecting ambient noise during audiometry testing.
  • Figure 13 assists in the derivation of the test stimulus prefilter required for the system shown in Figure 6 where a separate actuator is used to deliver the test stimulus and the control force.
  • Figure 14 shows the generalized design for a retroactively fit active noise control device which can be used with any audiometer.
  • Figure 15 shows a generalized design for an integrated active noise control audiometer where all of the components required for test stimulus delivery and active noise control are constructed into the same piece of hardware.
  • ANC active noise control
  • Active noise control uses an actuator, usually a speaker, to introduce into a noisy environment, a secondary sound pressure wave that is out of phase with the undesirable noise, or disturbance.
  • the anti-wave is generated electronically with some control algorithm whose input is a measure of the disturbance field. This measurement is usually performed by a microphone.
  • control approaches There are many configurations and designs for the control approaches that are application dependent. For the audiometry application, the goal is to provide a sound field at the user's ear that is quiet enough to measure a 0 dB hearing level (HL) for users with normal hearing acuity.
  • HL 0 dB hearing level
  • the audiometer In order to provide an accurate measurement, the audiometer must also provide a test stimulus with known SPL to the user's ear drum.
  • ANC in a disturbance rejection format, effectively improves the signal-to-noise ratio (SNR) of the test stimulus to ambient noise by reducing the ambient noise instead of amplifying the signal.
  • SNR signal-to-noise ratio
  • FIG 1 clearly illustrates the four main components of this innovation.
  • the passive performance (2) must work closely with the controller design and is often called the "plant” .
  • the plant design is discussed first, in detail, with specific reference to existing standards, passive noise control performance, and effects that the design has on active noise control in audiometry.
  • the controller (1) design is discussed. It can take on many forms including feedback, feedforward, and a combined feedback/feedforward approach.
  • the audiometer itself (3) may or may not be affected by the design of the controller and/or the plant. Methods for correcting any adverse effects are carefully explained since the audiometer must deliver the test stimulus to the user at a known SPL.
  • the summing junction (4) in Figure 1 is associated with the last component in the ANR audiometer design, i.e. the physical inclusion of the audiometer test signals in the ANR environment.
  • the "plant” is the system that the control acts upon. It includes all dynamics that exist between the output of the controller and the input to the controller. The plant is as critical to the control system design as the controller itself. Therefore, special emphasis is placed on the audiometry plant before discussing any controller approaches.
  • the passively controlled audiometry plant includes the input from the audiometer (6) (test stimulus) that drives the headplione speaker (7), the ambient noise disturbance d that is reduced by the passive control measure (5), the test subject's pinna (9). earcanal (9), and eardrum (10), and the test subject's response (12) detected by the audiometer.
  • a sensor is necessary to detect the disturbance so that the ANR control system can generate the anti-wave. Without loss of generality, it will be assumed that the sensor is a microphone placed near the subject's eardrum. This microphone placement is critical for many reasons that will be addressed momentarily.
  • FIG. 2b the audiometry plant that includes necessary control components.
  • the primary difference in Figure 2a and 2b is that there is an additional output (19).
  • the common output shown in the two figures is simply a qualitative measure of the subject ⁇ response to the audiometer stimulus signal.
  • the new output in Figure 2b is a quantitative measure of the sound pressure level inside the cavity created by the headphone and the subject's pinna. This measure is a linear combination of the passively controlled (12) disturbance and the test stimulus at the location of the microphone (19). It is clear that the microphone signal provides the input to the controller. By tracing the propagation of the controller output signal, the plant can be defined.
  • the output of an ANC controller is typically used to drive an electro-acoustic device such as a speaker.
  • the headphone speaker (14) shown in Figure 2b will also be used as the control actuator. Therefore the plant can be defined as the signal path including the dynamics of the headphone speaker (14), the cavity dynamics (16), and the microphone (19). Appropriate amplification of the controller output and microphone signals is also necessary but not mentioned here.
  • FIG. 3 illustrates an example of this concept with a speaker (actuator) (20), microphone ( sensor) (21) and subject (22).
  • Distance dj is small enough to be in the acoustic near field of the speaker (less than the radius of reverberation) while d2 is small enough to be less than the radius of the area of silence so that the highest desired frequency of noise reduction is perceivable by the test subject. Therefore, each of these distances is a function of the speaker size and ear canal depth, respectively.
  • both the actuator and sensor were fixed relative to the subject's head. This is typically in the form of a headset with a headband retaining both the left and right actuators. In the field of audiometry, this headband secures the headphone speakers onto the subject's ears with a specified force thereby creating a cavity in which the microphone sits. While it is clear that the microphone should be near the user's ear for reasons addressed above, it is possible that the actuators (speakers) could be located elsewhere. If these actuators were not affixed with respect to the sensor (affixed with respect to the user's ear), the plant dynamics could and would change with significant movement by the subject.
  • Figures 4a and 4b use two headphone actuators (24) that deliver both the control signal and audiometer test stimulus simultaneously, a sensor for each ear (25), and a headband (23) which secures the actuator sensor pair to the ears of the test subject.
  • Figure 4b uses two actuators: one for test stimulus delivery to each ear (27), and one set (26) for the active noise control force for each ear.
  • the standard actuator can be used along with the passive measures (MX style cushion) to perform ANC without deviating from the regulations.
  • MX style cushion the passive measures
  • the microphone must be placed so that the required volume of contact during the calibration procedure (6 cm-*) is not reduced by the presence of the microphone.
  • Figure 5 One possible headphone arrangement that meets ANSI and ISO standards is shown in Figure 5. The cross-section of a TDH headphone (29) equipped with a microphone (30) and MX cushion (28) places the microphone such that the calibration volume is the same before and after insertion of the microphone. There are many more possible arrangements that will meet the current audiometer standards by ensuring a proper cushion, seal, and calibration procedure.
  • the insert earphones require a slightly different approach if ANC is to be used directly with the insert earphone actuator.
  • the earphones fit into the subject's ear canal with a tube delivering the test stimulus to the eardrum.
  • This method provides unequaled passive performance in the high frequency region but cannot effectively block low frequency disturbances and is plagued with user variability as a result of non- repeatable insertion depths.
  • This drawback aside it is possible to place a microphone inside the foam plug that is inserted into the subject's ear. This is all that is required to perform active noise control with the foam plug. (The different control approaches are discussed shortly).
  • test signal actuator can be placed on the user's ear in accordance with the current standards. Then, an active noise control actuator-sensor pair can be placed in parallel with the test stimulus actuator. As will be seen later, depending on the control approach used, the test stimulus will likely be modified by the action of the controller. Using separate actuators can complicate the procedure required to compensate for this modification. This is explained in detail in the section describing the inclusion of the audiometer test stimulus. While this embodiment is not limited in application to either of the two traditional audiometer headphone devices, it will be most easily and effectively implemented with the insert earphones.
  • Figure 6 shows one possible embodiment of the dual actuator approach described above.
  • the insert earphone (34) is used to deliver the test stimulus (35) directly to the subject's ear drum (36) ana is effectively reducing ambient high frequency noise.
  • an active noise control headphone (33) having its own actuator (31) and sensor (32), is placed on top of the subject's pinna in order to provide low frequency attenuation.
  • compensation of the test sti ⁇ julus is necessary in some control approaches, specifically feedback control.
  • using separate actuators for insert earphone audiometry does not require test stimulus modification. This is considered to be a significant advantage. The reason for this is that the transfer function magnitude between the actuator delivery and the active noise control sensor is so small that the feedback control will not affect the test stimulus. This is shown in mathematical detail when the audiometer test stimulus delivery is described.
  • a headphone system that has superior passive performance and incorporates active noise control, can be designed to deliver a known SPL to a subject's eardrum.
  • the cross section of one such device is shown in Figure 7.
  • a larger volume (40) is provided to easily house the ANC sensor (38) and to bring it equally close to the subject s ear and speaker.
  • a circum-aural passive seal (39) is provided which more effectively attenuates high frequencies than the conventional supraural cushion.
  • a design such as this will improve both active and passive performance but will likely not meet applicable standards due to the circum-aural contact and excess volume in front of the speaker.
  • a new calibration procedure is proposed for this system by first determining the average subject's eardrum location and enclosed volume. Then each test tone can be calibrated with an SPL meter located at the virtual average eardrum in a fixture that approximates the average human skull, pinna, ear canal combination. This is precisely the same procedure used to calibrate the current standard; it is simply an estimate of the average human's auditory frequency response characteristics.
  • FIG. 8 illustrates a block diagram of a conventional feedback control loop.
  • the plant G(s) (42) contains all of the dynamics described earlier for the active noise control system while H(s) (43) represents the controller itself.
  • the disturbance d(t) represents the undesirable ambient noise entering the system just following the plant.
  • the input signal t(t) is the test stimulus
  • the output e(t) of the entire (closed-loop) system represents the sound pressure level experienced by the user and is also the input to the controller.
  • the leedb'ack controller design itself is quite simple.
  • Each transfer function in the block diagram is a function of Trequency, represented using the Laplace variable "s" .
  • a mathematical expression for the time signal e(t) as a function of the signals d(t) and t(t) can be created assuming negative feedback and is shown below.
  • test stimulus is adversely affected by the closed loop system. It is desired to have the coefficient of the test stimulus t(t) equal to unity for all frequencies so the SPL delivered to the subject 'e(t)), is known. In order to achieve this, P(s), a pre-filter for the test stimulus must be
  • P(s) shown above will represent an acausal or unrealizable filter with a zero-pole excess.
  • a filter can be built that minimizes or eliminates the control loop's effects on the test stimulus. This is achieved by designing P(s) as shown above, over a narrow bandwidth of the test stimulus and subsequently adding higher (outside the test stimulus bandwidth) frequency poles.
  • FIG. 9 shows a detailed block diagram of a closed loop feedback controlled system for disturbance rejection in audiometry using analog electronics only.
  • the analog filters P(s) (45) and ⁇ (s) (49) are built using operational amplifiers, resistors, and capacitors to place the zeros and poles of F(s) and H(s).
  • the components include signal amplifiers (46)(50), the speaker (47), microphone (51) and cavity (48).
  • Figure 10 shows an entirely different implementation of feedback disturbance rejection for audiometry, realized using digital software.
  • H(z) (61) and P(z) (55) are digital filters designed under the same Bode gain and phase constraints discussed above, implemented using FIR or IIR filters in DSP software.
  • FIG. 11 illustrates the feedforward control approach for active noise control in audiometry. Because of the complexity of the algorithm, it is not possible to efficiently implement the feedforward controller using only analog hardware, so only the digital implementation for audiometry is shown. Beginning with the controller itself (72)(79), the general structure is commonly known as the filtered-X LMS algorithm used in active noise control. The software based algorithm (79) computes the weights (filter coefficients) for the FIR filter (72) using either the standard LMS algorithm or the "leaky" LMS algorithm, shown respectively below
  • w(n + 1) w(n) + ⁇ r(n)e (n)
  • the weights (w(n)) are calculated during each sample iteration based on the measurement of the reference signal r(n) and the error signal e(n).
  • the error signal is the same as in feedback control, collected from the error sensor (microphone) (83) near the subject's ear.
  • the reference signal is a signal that is highly correlated with the error signal but not controllable by the control actuator, or speaker (76). (This prevents a feedback loop that can go unstable).
  • the selection of this reference signal for active noise control is most commonly a secondary microphone located at a distance far enough away from the speaker that the frequency response function magnitude from the speaker to the reference microphone is lower than -20 dB at all frequencies.
  • the factor u controls the rate of convergence of the filter and should be less than the inverse oi the average reference signal power. This constitutes the stability constraint in feedforward control. If this value is too high, the algorithm will diverge by taking too large of an increment between weight calculations. If it is too small, convergence will not be fast enough for changing noise field dynamics. Finally, the "forgetting factor" in the leaky LMS algorithm allows old, non-useful weight update information to be lost over time. This is useful when transient noises impinge on both the reference signal and the error signal but need not be controlled over long periods of time.
  • This combined signal is then used to drive a single actuator (76) that delivers both the control and test stimulus.
  • the third and final option (not explicitly shown) for delivery of the test stimulus is to generate the stimulus from within the control code and add it to the computed control signal. This provides the most flexibility for inclusion of software analysis, display, and control options and allows the DSP to perform the entire ANC audiometry task.
  • feedforward control is most effective for controlling tonal sound fields because the correlation between the reference signal and error signal is highest for sinusoidal waveforms. Since conventional feedforward control is not bounded by the stability constraints of feedback control, theoretical performance is only limited by the correlation between the reference and error signals. For very high coherence, feedforward performance is unbounded. Feedback control however, has limited levels of performance over a pre-specified bandwidth as determined by the Bode gain phase relationship. For these reasons, feedback control tends to perform better for broadband and " ⁇ at" noise fields while feedforward control performs better for tonal noise fields. In reality, most ambient noise fields contain a combination of broadband and tonal content. Therefore, the best choice for a controller that can effectively reject these disturbances is a combination of feedback and feedforward control.
  • the audiometer application may require the blended approach depending on the ambient noise environment, so it is specified in this description.
  • Figure 12 illustrates a block diagram of the combination feedback and feedforward control approach for audiometry.
  • Several of the details presented for the individual control approaches still apply to Figure 12 even though they are not explicitly shown. (These include the microphone, amplifiers, cavity and speaker represented by G(s) (86) and the anti-alias and smoothing filters required in the sampling process).
  • the feedback controller (84) In order to combine these two control approaches, the feedback controller (84) must be in place before the feedforward controller (87)(89) is designed. This is primarily because the system identification required by the filtered reference (88) LMS algorithm (89) changes when the controller is included in the loop. (Although Figure 12 shows the feedback controller in an analog implementation, the combined controller can also be entirely digital).
  • the system ID for the feedforward controller can take place.
  • the output of the feedback controller is added directly to the output of the feedforward controller to form a single control signal that is sent to the actuator.
  • the test stimulus is also combined with the control force and sent to the same actuator if only a single actuator is used for both control and test signals.
  • the pre-filter (85)for the test stimulus is to compensate for the feedback portion of the combined controller only.
  • the feedforward control approach has no effect on the test stimulus as long as it is not present in the reference signal.
  • the two voltages are combined using a summing junction realized in analog hardware (operation amplifiers) or in digital software code.
  • the pre-filter necessary for the test stimulus must cover the same bandwidth as the test stimulus and invert the closed loop control system to ensure that the test stimulus remains unaffected.
  • the required pre-filter becomes a function of the dynamics between the actuator delivering the test stimulus and the error sensor in active noise control.
  • the test stimulus behaves as part of the disturbance that the closed loop controller is attempting to cancel.
  • Gj(s (90) is very small, the transfer function coefficient becomes unity and the pre-filter P(s) (97) can also be unity in order to deliver t(t) to the eardrum unaffected.
  • P(s) is non-unity and must be designed to invert the coefficient of t(t) in the equation above, over the bandwidth of the test stimulus.
  • Feedforward control offers a distinct advantage over feedback for ANR audiometry in that the test stimulus can be delivered to the subject unaffected by the control action, without any additional modifications.
  • the error sensor microphone
  • the error sensor should be located close to the subject's ear to maximize noise control performance.
  • the reference sensor does not detect or contain signal content from the test stimulus (i.e. coherence is low)
  • the feedforward controller will have no effect on the test stimulus.
  • the combined feedback and feedforward control option will only require modification as a result of the feedback control force, and not the feedforward.
  • the equation above will apply since the feedforward control action will have no affect on the test stimulus.
  • the primary requirement for delivery of the test stimulus is that the SPL at the eardrum needs to be known. This allows an accurate comparison of hearing levels to those with normal hearing at 0 dB HL (established over many years of testing).
  • the goal of modifying the test stimulus with a pre-filter is to deliver the signal without modification so calibration baselines can be established as they always have been.
  • the baseline could be established for the test stimulus during the calibration procedure, thus eliminating the need for a pre-filter. This works especially well for narrow band test stimuli such as pure tones. An example of this is now presented for clarity.
  • the pre-filter required for a pure tone test stimulus is one frequency unit wide and corresponds to a simple gain. With the pre- filter in place, the calibration setting for the pure tone under test, before and after the inclusion of the ANC will not differ since the SPL of the tone has been adjusted to remain the same. However, if the pre-filter is removed, the SPL of the test stimulus will be much lower due to the closed loop control action. Calibration of the SPL of the test tone will be different for the control on vs. control off case. If the test tone is reduced by 20 dB due to the control action, the calibration of the measured hearing level can be adjusted by adding 20 dB, thus eliminating the need for a pre-filter. For broad band test stimuli such as speech, the calibration procedure will not be as effective in determining accurate thresholds due to the need for frequency dependent gain.
  • test signal has been included into the control algorithm, a decision must be made on how to properly incorporate the audiometer hardware or software with the ANC hardware or soltware.
  • the ANC retro-fit device includes the ANC headphone system (101)(102), an input output device (100)(99) containing the ANC hardware or software (depending on the control approach used), and two cables to connect the standard audiometer to the ANC device.
  • the left and right ear testing cables are separate one-channel lines (as opposed to a single two-channel line). Either embodiment is possible depending on the output of the audiometer.
  • the ANC device receives as its input, the left and right audiometer signals that are sent to the pre-filters (if required) as described above. These signal inputs must be impedance matched.
  • the stimulus delivery system cannot be the conventional headphone system delivered with the standard audiometer.
  • the headphone system (101)(102) will conform to the plant design requirements presented above for ANC audiometry, but may be any embodiment that has been described and still apply to this retro-fit device.
  • the two inputs are the left ear and right ear microphones (102) and the outputs are the left ear and right ear actuators (101). If a dual actuator approach is used, the test stimulus can either be pre-filtered by the ANC device (requiring two more outputs) or passed directly to the test stimulus delivery actuator if pre-filtering is not required.
  • ANC retro-fit device could include a reference signal for use in feedforward or combined feedforward and feedback control.
  • This embodiment permits clinicians with experience and access to - a conventional audiometer (98), to take advantage of the benefits of an ANC audiometer.
  • the next embodiment gives the consumer the opportunity to upgrade their entire audiometer system.
  • An integrated ANC audiometer combines into a single package, both the ANC hardware and audiometry hardware as shown in Figure 15.
  • all the functions of the ANC system (105) describe ⁇ above are constructed as integral electronics with the audiometer function electronics (106) within a common casing.
  • the user will be able to switch on or off the ANR functionality depending on the environmental noise conditions.
  • the ANR circuitry will provide the required additional noise reduction.
  • This integrated configuration of the audiometer can be used as a single unit without need for external attachments of any type. It will require the use of a special headphone system (103)(104) of the construction and functionality described in detail above.

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Abstract

La technologie de la réduction active de bruit (ANR) est incorporée dans les essais audiométriques sous diverses formes. Les mécanismes de contrôle de bruit par la rétroaction adaptative, la correction aval adaptative, la rétroaction numérique et rétroaction analogique, sont présentés en vue d'une utilisation audiométrique de façon à réduire le bruit ambiant entendu par le sujet étudié, permettant d'étudier des sujets dans des champs sonores ambiants plus élevés. Les signaux d'essai des audiomètres sont correctement compensés de sorte que les résultats de l'essai soient précis et conformes aux normes d'étalonnage existantes en audiométrie, et de sorte que l'on puisse effectuer la réduction active de bruit tout en satisfaisant aux normes existantes des essais audiométriques . On utilise un audiomètre (6) avec un haut parleur de casque (7) permettant d'étudier la membrane du tympan (10).
PCT/US1999/016293 1999-07-26 1999-07-26 Reduction active de bruit pour audiometrie WO2001006916A1 (fr)

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Cited By (9)

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EP1516584A1 (fr) * 2003-09-17 2005-03-23 Siemens Audiologische Technik GmbH Dispositif et méthode pour détermination d'une gamme d'audibilité
US7288072B2 (en) 2002-05-23 2007-10-30 Tympany, Inc. User interface for automated diagnostic hearing test
US7736321B2 (en) 2003-05-15 2010-06-15 Tympany, Llc Computer-assisted diagnostic hearing test
US8366632B2 (en) 2002-05-23 2013-02-05 Tympany, Llc Stenger screening in automated diagnostic hearing test
US8394032B2 (en) 2002-05-23 2013-03-12 Tympany Llc Interpretive report in automated diagnostic hearing test
US10368785B2 (en) 2008-10-24 2019-08-06 East Carolina University In-ear hearing test probe devices and methods and systems using same
US11924612B2 (en) 2017-10-05 2024-03-05 Cochlear Limited Distraction remediation at a hearing device

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