Systems and methods for eliciting a stapedial reflex to protect hearing

An exemplary system includes 1) a sound detector configured to detect an audio signal, 2) an implantable stimulator configured to be implanted within a user, and 3) a sound processor communicatively coupled to the implantable cochlear stimulator and the sound detector. The sound processor is configured to determine that a level of the audio signal exceeds a predetermined threshold and direct, in response to the determination that the level of the audio signal exceeds the predetermined threshold, the implantable stimulator to elicit a stapedial reflex within the user by applying electrical stimulation to one or more stimulation sites within the user. Corresponding systems and methods are also disclosed.

BACKGROUND INFORMATION

The natural sense of hearing in human beings involves the use of hair cells in the cochlea that convert or transduce acoustic signals into auditory nerve impulses. Hearing loss, which may be due to many different causes, is generally of two types: conductive and sensorineural. Some types of conductive hearing loss occur when the normal mechanical pathways for sound to reach the hair cells in the cochlea are impeded. These sound pathways may be impeded, for example, by damage to the auditory ossicles. Conductive hearing loss may often be overcome through the use of conventional hearing aids that amplify sound so that acoustic signals can reach the hair cells within the cochlea. Some types of conductive hearing loss may also be treated by surgical procedures.

Sensorineural hearing loss, on the other hand, is caused by the absence or destruction of the hair cells in the cochlea, which are needed to transduce acoustic signals into auditory nerve impulses. People who suffer from severe to profound sensorineural hearing loss may be unable to derive significant benefit from conventional hearing aid systems, no matter how loud the acoustic stimulus. This is because the mechanism for transducing sound energy into auditory nerve impulses has been damaged. Thus, in the absence of properly functioning hair cells, auditory nerve impulses cannot be generated directly from sounds.

To overcome sensorineural hearing loss, numerous cochlear implant systems—or cochlear prostheses—have been developed. Cochlear implant systems bypass the hair cells in the cochlea by presenting electrical stimulation directly to the auditory nerve fibers. Direct stimulation of the auditory nerve fibers leads to the perception of sound in the brain and at least partial restoration of hearing function.

In many people with sensorineural hearing loss, the hair cells deep within the cochlea that sense low frequencies are substantially undamaged. Such people may be able to hear low frequencies without assistance or by means of an amplifying hearing aid. However, due to impaired hearing, the remaining low frequency hearing may be vulnerable to accelerated deterioration. In particular, loss of hearing may increase the stapedial reflex threshold (“SRT”) of a person. The SRT is the loudness at which the brain will cause the stapedial muscle to contract thereby applying tension to the ossicles of the inner ear and reducing the amplitude of vibrations reaching the cochlea by up to 25 dB. As the SRT rises, the low frequency hair cells of the cochlea are exposed to higher intensity vibrations for longer periods of time, thereby accelerating hearing loss and exposing the person to potentially damaging effects caused by sounds with relatively high intensity levels.

DETAILED DESCRIPTION

Systems and methods for eliciting a stapedial reflex of a user in order to protect hearing are described herein. An exemplary system includes a sound detector configured to detect an audio signal, an implantable stimulator configured to be implanted within a user, and a sound processor communicatively coupled to the implantable stimulator and the sound detector. The sound processor is configured to determine that a level of the audio signal exceeds a predetermined threshold, and, in response, direct the implantable stimulator to elicit a stapedial reflex within the user by applying electrical stimulation to one or more stimulation sites within the user.

In one exemplary implementation, the system includes a stapedial electrode communicatively coupled to the implantable stimulator and configured to be coupled to at least one of a stapedius tendon and a stapedius muscle of the user. In this implementation, the sound processor may be further configured to direct the implantable stimulator to elicit the stapedial reflex by applying the electrical stimulation to at least one of the stapedius tendon and the stapedius muscle by way of the stapedial electrode.

In another exemplary implementation, the system includes an intracochlear electrode array communicatively coupled to the implantable stimulator and configured to be implanted within a cochlea of the user. In this implementation, the sound processor may be further configured to direct the implantable stimulator to elicit the stapedial reflex by applying the electrical stimulation to one or more locations within the cochlea by way of the intracochlear electrode array. In some examples, only high-frequency electrodes (i.e., electrodes corresponding to a relatively high frequency band, such as frequencies greater than 1000 Hz) of the intracochlear electrode array are stimulated to elicit the stapedial reflex.

By electrically eliciting a stapedial reflex in response to detecting audio signals that have a level (e.g., a sound pressure level (“SPL”), a volume level, an intensity level, etc.) that exceeds a predetermined threshold, the systems and methods herein may help protect (e.g., preserve) a user's hearing (e.g., any hearing ability that the user may have, such as low frequency residual hearing that an electro-acoustic stimulation (“EAS”) user may have). For example, by detecting that an incoming audio signal (e.g., an explosion, blast, or other noise) is relatively loud, the systems and methods herein may elicit a stapedial reflex in a manner that is “on-demand” (i.e., prior to the audio signal being processed by ears and/or brain of the user) and thereby force the stapedius muscle to be in a contracted state while the incoming audio signal is processed by the user. This may preserve hearing (e.g., residual hearing) in the user and/or otherwise protect the user from one or more damaging effects of the audio signals. Other benefits and/or advantages provided by the disclosed systems and methods will be made apparent herein.

FIG. 1illustrates an exemplary hearing protection system100that may be configured to protect hearing in a user (i.e., a user of hearing protection system100). Hearing protection system100may include a sound detector102, a sound processor104, an implantable stimulator106, and a stapedial electrode108. Additional or alternative components may be included within hearing protection system100as may serve a particular implementation.

As shown, hearing protection system100may include various components configured to be located external to a user including, but not limited to, a sound detector102and sound processor104. Hearing protection system100may further include various components configured to be implanted within the user including, but not limited to, the implantable stimulator106coupled to the stapedial electrode108. The stapedial electrode108may be coupled to a stapedius tendon, stapedius muscle, and/or an area of a user's inner ear proximate either of these members such that electrical stimulation can be applied to the stapedius muscle. As will be described in more detail below, additional or alternative components may be included within hearing protection system100as may serve a particular implementation. The components shown inFIG. 1will now be described in more detail.

Sound detector102may be configured to detect audio signals presented to the user. Sound detector102may be implemented in any suitable manner. For example, sound detector102may include a microphone (e.g., a “T-Mic” or the like) that is configured to be placed within the concha of the ear near the entrance to the ear canal. Such a microphone may be held within the concha of the ear near the entrance of the ear canal by a boom or stalk that is attached to an ear hook configured to be selectively attached to sound processor104. Additionally or alternatively, sound detector102may be implemented by one or more microphones disposed within sound processor104and/or any other suitable microphone as may serve a particular implementation.

As will be described in greater detail below, the exemplary implementations disclosed herein are particularly useful for eliciting the stapedial reflex of users in response to loud noises. Accordingly, the sound detector102in the embodiment ofFIG. 1may, in some embodiments, include no more functionality than required to detect very loud sounds (e.g., sounds having a loudness level near a stapedial reflex threshold (“SRT”) or some other arbitrary loudness threshold). Accordingly, sound detector102may include a microphone capable of detecting sound and outputting a signal representing that sound or as a device that produces an output in response to a loud sound that is not necessarily a faithful reproduction of the amplitude and/or frequency content of the loud sound. For example, a sound detector102may be embodied as an accelerometer, piezoelectric transducer, strain gauge, load cell, or any other device capable of detecting displacement or vibration due to a loud noise but not necessarily capable of accurately representing received sound in an output thereof sufficient to use the output to provide hearing assistance to the user.

In some exemplary implementations, the hearing protection system100ofFIG. 1may be used by those without hearing loss in order to preserve hearing. For example, people who work around loud noises may use the illustrated hearing protection system100to prevent hearing loss that may be caused by the loud noises. In particular, members of the military who work in bomb disposal or are otherwise proximate explosions and/or gunfire may be reluctant to wear hearing protection in a hostile environment due to the loss of awareness to threats. Accordingly, such individuals or others may use the hearing protection system100ofFIG. 1in order to provide hearing protection when needed.

Sound processor104(i.e., one or more components included within sound processor104) may be configured to direct implantable stimulator106to generate and apply electrical stimulation (also referred to herein as “stimulation current”) in response to one or more audio signals (e.g., one or more audio signals detected by sound detector102, input by way of an input port, etc.) to one or more of a stapedius muscle, stapedius tendon, or adjacent area by means of the stapedial electrode108. Sound processor104shown inFIG. 1may include or be implemented by a behind-the-ear (“BTE”) unit, a relatively small monitor, a body worn device, and/or any other sound processing unit as may serve a particular implementation.

In the exemplary implementation ofFIG. 1, sound processor104may be configured to perform threshold detection with respect to an output of the sound detector102. For example, sound processor104may be configured to determine whether a level (e.g., an SPL, a volume level, an intensity level, a power level, etc.) of an audio signal detected by sound detector102exceeds a predetermined threshold (e.g., a threshold SPL, a threshold volume level, a threshold intensity level, a threshold power level, etc.). This may be performed in any suitable manner.

For example, sound processor104may determine that the level of the audio signal exceeds the predetermined threshold by evaluating one or more of a voltage, current, and power level of an electrical output of sound detector102and determining that any of these levels are above a corresponding voltage threshold level, a corresponding current level, or a corresponding power level. In some examples, the threshold comparison may be performed by analog circuitry capable of performing threshold detection. Additionally or alternatively, the threshold comparison may be performed digitally by a programmable processor, digital signal processor (“DSP”), or other digital device.

As another example, sound processor104may determine that the level of the audio signal exceeds the predetermined threshold by detecting (e.g., predicting) that the level of the audio signal is going to exceed the predetermined threshold before the audio signal actually exceeds the predetermined threshold. For example, sound processor104may determine that a slope of an increase in the audio signal exceeds a predetermined slope. This may indicate that the audio signal is rapidly increasing in amplitude, for example, and that it will soon exceed the predetermined threshold. Other ways of determining that the level of the audio signal is going to exceed the predetermined threshold before the audio signal actually exceeds the predetermined threshold are described in U.S. Pat. No. 7,983,425, the contents of which are hereby incorporated by reference in their entirety.

By detecting that the level of the audio signal is going to exceed the predetermined threshold before the audio signal actually exceeds the predetermined threshold, sound processor104may have relatively more time to elicit a stapedial reflex that protect the user's hearing from any damaging effects that the audio signal may cause.

In response to a determination that the level of the audio signal exceeds the predetermined threshold, sound processor104may direct implantable stimulator106to elicit a stapedial reflex within the user by applying electrical stimulation to one or more stimulation sites within the user. For example, in the configuration ofFIG. 1, sound processor104may direct implantable stimulator106to elicit the stapedial reflex by applying electrical stimulation to the stapedius muscle and/or stapedius tendon by way of stapedial electrode108. This may be performed in any suitable manner. For example, sound processor104may generate an excitation signal and transmit this signal over a communication link110to the implantable stimulator106, which then generates the electrical stimulation in accordance with the amplitude and/or frequency of the excitation signal. Alternatively, sound processor104may generate a drive signal (e.g., a signal that includes one or more stimulation parameters) that is transmitted to the implantable stimulator106, which then responds to the drive signal by generating the stimulation current (e.g., in accordance with one or more stimulation parameters included in the drive signal).

The stimulation current applied by implantable stimulator106to stapedial electrode108may be configured to elicit the stapedial reflex of the user, i.e., cause contraction of the stapedius muscle. The stimulation current may be a direct current or alternating current signal and may have attributes such as amplitude, frequency, duty cycle, pulse width, and the like, effective to cause contraction of the stapedius muscle without damaging the stapedius muscle, stapedius tendon, or surrounding tissues.

In some examples, sound processor104may wirelessly transmit signals (e.g., excitation signals, drive signals, stimulation parameters (e.g., in the form of data words included in a forward telemetry sequence or analog signals), and/or power signals) to implantable stimulator106by way of wireless communication link110. It will be understood that communication link110may include a bi-directional communication link and/or one or more dedicated uni-directional communication links. For example, communication link110may be implemented by sound processor104and implantable stimulator106by means of inductive coils, capacitive plates, radio frequency antennas, and/or any other structure for generating or receiving an electromagnetic field and corresponding circuits for interfacing with any of these structures.

Implantable stimulator106shown inFIG. 1may include any type of implantable stimulator that may be used in association with the systems and methods described herein. For example, implantable stimulator106may include a relatively small intra-ear canal device (e.g., an actuator) configured to provide electrical stimulation by way of one or more electrodes coupled thereto. Such a device may be beneficial to users who would like to avail themselves of the features described herein while minimizing the surgical invasiveness that may occur with respect to larger types of implantable stimulators. Alternatively, as will be described below, implantable stimulator106may be implemented by a cochlear implant or the like that is configured to generate stimulation current representative of an audio signal processed by sound processor104(e.g., an audio signal detected by sound detector102) in accordance with one or more stimulation parameters transmitted thereto by sound processor104. Implantable stimulator106may be further coupled to the stapedial electrode108, such as by means of a lead112.

FIG. 2illustrates another exemplary hearing protection system200that may be configured to protect hearing in a user (i.e., a user of hearing protection system200). Hearing protection system200is similar to hearing protection system100in that it includes sound detector102, sound processor104, and implantable stimulator106. However, as shown, hearing protection system200may additionally include a headpiece202and a lead204with a plurality of electrodes206disposed thereon, the plurality of electrodes defining an intracochlear electrode array. Hence, hearing protection system200may also be referred to as a cochlear implant system. Additional or alternative components may be included within hearing protection system100as may serve a particular implementation.

In the exemplary implementation ofFIG. 2, sound processor104(i.e., one or more components included within sound processor104) may be configured to direct implantable stimulator106to generate and apply electrical stimulation representative of one or more audio signals (e.g., one or more audio signals detected by sound detector102, input by way of an auxiliary audio input port, etc.) to one or more stimulation sites associated with an auditory pathway (e.g., the auditory nerve) of the user. Exemplary stimulation sites include, but are not limited to, one or more locations within the cochlea, the cochlear nucleus, the inferior colliculus, and/or any other nuclei in the auditory pathway. To this end, sound processor104may process the one or more audio signals in accordance with a selected sound processing strategy or program to generate appropriate stimulation parameters for controlling implantable stimulator106. Sound processor104shown inFIG. 2may include or be implemented by a behind-the-ear (“BTE”) unit, a body worn device, and/or any other sound processing unit as may serve a particular implementation.

Headpiece202may be communicatively coupled to sound processor104and may include an external antenna (e.g., a coil and/or one or more wireless communication components) configured to facilitate selective wireless coupling of sound processor104to implantable stimulator106. Headpiece202may be additionally or alternatively be used to selectively and wirelessly couple any other external device to implantable stimulator106. To this end, headpiece202may be configured to be affixed to the user's head and positioned such that the external antenna housed within headpiece202is communicatively coupled to a corresponding implantable antenna (which may also be implemented by a coil and/or one or more wireless communication components) included within or otherwise associated with implantable stimulator106. In this manner, stimulation parameters and/or power signals may be wirelessly transmitted between sound processor104and implantable stimulator106via the communication link110.

Implantable stimulator106shown inFIG. 2may include any type of implantable stimulator that may be used in association with the systems and methods described herein. For example, implantable stimulator106may be implemented by an implantable cochlear stimulator. In some alternative implementations, implantable stimulator106may include a brainstem implant and/or any other type of cochlear implant that may be implanted within a user and configured to apply stimulation to one or more stimulation sites located along an auditory pathway of a user.

In some examples, implantable stimulator106may be configured to generate electrical stimulation representative of an audio signal processed by sound processor104(e.g., an audio signal detected by sound detector102) in accordance with one or more stimulation parameters transmitted thereto by sound processor104. Implantable stimulator106may be further configured to apply the electrical stimulation to one or more stimulation sites within the user via one or more electrodes206disposed along lead204. In some examples, implantable stimulator106may include a plurality of independent current sources each associated with a channel defined by one or more of electrodes206. In this manner, different stimulation current levels may be applied to multiple stimulation sites simultaneously by way of multiple electrodes206.

In some examples, in response to a determination that a level of an audio signal exceeds a predetermined threshold, sound processor104may direct implantable stimulator106to elicit a stapedial reflex by applying electrical stimulation to one or more locations within the cochlea of the user by way of one or more electrodes206(i.e., by way of an intracochlear electrode array). To ensure that a stapedius reflex is elicited in response to the electrical stimulation, the electrical stimulation may have a current level substantially equal to a most comfortable current level (“M level”) associated with the user.

Sound processor104may be further configured to protect the user from damaging effects of a high level audio signal by abstaining from directing implantable stimulator106to apply electrical stimulation representative of the audio signal by way of one or more electrodes206(e.g., by bypassing some or all of the sound processing functionality of sound processor104, as will be described in more detail below). For example, as described above, in response determining that the level of an audio signal exceeds a predetermined threshold, sound processor104may direct implantable stimulator106to elicit a stapedial reflex by applying electrical stimulation to one or more locations within the cochlea of the user by way of one or more electrodes206. However, sound processor104may abstain from directing implantable stimulator106to apply additional electrical stimulation that is representative of the audio signal by way of electrodes206. In this manner, sound processor104may prevent damage that may be caused by applying electrical stimulation representative of the high level audio signal. Alternatively, sound processor104may attenuate the audio signal prior to directing implantable stimulator106to apply electrical stimulation representative of the audio signal to the user.

FIG. 3illustrates another exemplary hearing protection system300that may be used in accordance with the systems and methods described herein. As shown, hearing protection system300includes both a stapedial electrode108and an intracochlear electrode array (i.e., electrodes206). In this configuration, sound processor104may direct implantable stimulator106to elicit a stapedius reflex by applying electrical stimulation to the stapedius muscle and/or stapedius tendon by way of stapedial electrode108and/or by applying electrical stimulation to one or more stimulation sites within the cochlea by way of one or more of electrodes206.

FIG. 4illustrates another hearing protection system400that may be used in accordance with the systems and methods described herein. Hearing protection system400is similar to hearing protection system200, except that hearing protection system100further includes a receiver402(which may be implemented as a loudspeaker or insert earphone) configured to provide acoustic stimulation to the user. Hence, hearing protection system400may be referred to as an electro-acoustic stimulation (“EAS”) system.

Hearing protection system400may be used by users who have some degree of low frequency residual hearing (e.g., below 1000 Hz). For example, sound processor104may be configured to direct receiver402to apply acoustic stimulation representative of audio content included in a relatively low frequency band (e.g., below 1000 Hz) to the user and implantable stimulator106to apply electrical stimulation representative of audio content included in a relatively high frequency band (e.g., above 1000 Hz) to one or more stimulation sites within the user by way of one or more of electrodes206.

In the configuration shown inFIG. 4, sound processor104may be configured to direct implantable stimulator106to elicit a stapedius reflex in response to a determination that a level of an audio signal exceeds a predetermined threshold in any of the ways described herein. For example, sound processor104may direct implantable stimulator106to elicit a stapedial reflex by applying electrical stimulation to one or more locations within the cochlea of the user by way of one or more electrodes206. In some embodiments, hearing protection system400may further include stapedial electrode108, which may also be used to electrically elicit the stapedius reflex.

In some examples, sound processor104may additionally or alternatively elicit a stapedial reflex to protect hearing by applying acoustic stimulation to the user by way of receiver402. The acoustic stimulation may have any suitable characteristic as may serve a particular implementation. For example, the acoustic stimulation may include a relatively low frequency tone burst (e.g., a 125 Hz tone burst).

By electrically and/or acoustically eliciting a stapedius reflex in an EAS user in response to a determination that an incoming audio signal has a relatively high level, hearing protection system400may assist in preserving the EAS user's residual low frequency hearing.

FIG. 5illustrates exemplary components of implantable stimulator106. As shown inFIG. 5, implantable stimulator106may include a communication facility502, a current generation facility504, a stimulation facility506, and a stapedial stimulation facility508, which may be in communication with one another using any suitable communication technologies. Each of these facilities502-508may include any combination of hardware, software, and/or firmware as may serve a particular application. For example, one or more of facilities502-508may include a computing device or processor configured to perform one or more of the functions described herein. Facilities502-508will now be described in more detail.

Communication facility502may be configured to facilitate communication between implantable stimulator106and sound processor104. For example, communication facility502may include one or more coils configured to receive control signals and/or power via one or more communication links110to implantable stimulator106.

Current generation facility504may be configured to generate stimulation current in accordance with one or more stimulation parameters received from sound processor104. To this end, current generation facility504may include one or more current generators and/or any other circuitry configured to generate stimulation current. For example, current generation facility504may include an array of independent current generators each corresponding to a distinct electrode206or channel. For exemplary hearing protection systems that include stapedial electrode108, current generation facility504may additionally or alternatively include a current generator configured to generate stimulation current for application to the stapedial electrode108responsive to control signals from the sound processor104.

Stimulation facility506may be configured to facilitate application of the stimulation current generated by current generation facility504to one or more stimulation sites within the user in accordance with one or more stimulation parameters received from sound processor104. To this end, stimulation facility506may be configured to interface with the one or more electrodes206by means of the lead204. For hearing protection systems that include a stapedial electrode108, stimulation facility506may additionally or alternatively be configured to facilitate application of the stimulation current generated by current generation facility504to the stapedial electrode108.

The exemplary implementations described herein advantageously provide means to stimulate the stapedial reflex of a user in response to loud noises such that the user's hearing may be protected (e.g., by preserving an ability of the user to hear normally, preserving the user's residual hearing, etc.). In order to improve the degree of protection, the stimulation of the stapedius muscle may occur as soon as possible in order to reduce the amount of time that the cochlea of the user is exposed to vibrations without damping due to the stapedial reflex.

Accordingly, in some exemplary implementations, implantable stimulator106may include a stapedial stimulation facility508to more quickly stimulate the stapedial electrode108. The stapedial stimulation facility508may define a separate path for control signals from the sound processor104directing stimulation of the stapedial electrode108to be translated into current applied to the stapedial electrode108. In other examples, the stapedial stimulation facility508is omitted and stimulation current for the stapedial electrode108is generated in the same manner using the same facilities502-508as used to stimulate the electrodes206. The stapedial stimulation facility508may include one or both of separate hardware paths and separate software paths in the data/signal flow by which a control signal received over the communication link110is translated into a current applied to the lead112of the stapedial electrode108by the implantable stimulator.

FIG. 6illustrates exemplary components of sound processor104. As shown inFIG. 6, sound processor104may include a communication facility602, a processing facility604, a threshold facility606, and a bypass facility608, any or all of which may be in communication with one another using any suitable communication technologies. Each of these facilities602-608may include or be implemented by any combination of hardware, software, and/or firmware as may serve a particular application. For example, one or more of facilities602-608may include or be implemented by a computing device or processor configured to perform one or more of the functions described herein. It will also be recognized that one or more of facilities602-608may be optionally not included within sound processor104. Facilities602-608will now be described in more detail.

Communication facility602may be configured to facilitate communication between sound processor104and implantable stimulator106. For example, communication facility602may include transceiver components configured to wirelessly transmit data (e.g., control parameters and/or power signals) to implantable stimulator106by way of a coil included in headpiece202.

Processing facility604may be configured to perform one or more signal processing heuristics on an audio signal presented to the user, such as an output of sound detector102. For example, processing facility604may perform one or more pre-processing operations, spectral analysis operations, noise reduction operations, mapping operations, and/or any other types of signal processing operations on a detected audio signal as may serve a particular application. In some examples, processing facility604may generate one or more control parameters governing an operation of implantable stimulator106(e.g., one or more stimulation parameters defining the electrical stimulation to be generated and applied by implantable stimulator106).

Threshold facility606may be configured to evaluate an output of the sound detector102with respect to a threshold. The threshold may correspond to an estimate of a level such that for sound below that level no significant loss of hearing will occur and sound above that level will cause loss of hearing. In some examples, the threshold facility606is configured to sample the output of the sound detector102periodically and compare the sample to the threshold. For example, the processing facility may sample an output of the sound detector102and convert the samples to binary values. Threshold facility606may then periodically sample these binary values.

In a healthy person, the time between the commencement of an above-SRT sound and the stapedial reflex is about 10 to 20 ms. However, in many instances, this response time is too slow to prevent substantial damage to a person's hearing. In particular, for a person with hearing loss, the loudness at which the stapedial reflex is elicited is higher than the loudness above which hearing damage occurs, even with use of a hearing protection system, such as any of the hearing protection systems described herein. Accordingly, the hearing protection systems described herein may advantageously elicit the stapedial reflex both faster and at a lower loudness threshold than the naturally occurring stapedial reflex of the user.

To that end, the sampling period for threshold facility606may be substantially smaller than 10 to 20 ms. In general, the sampling period may be as short as possible without perceptibly degrading the quality of hearing assistance provided by the hearing protection systems described herein due to interruption of the processing facility604. For example, the sampling period may be between 5 μs and 1 ms (e.g., 10 μs). Stated differently, the threshold facility606may sample one of every N digital samples from the output of the sound detector102, where N is chosen to be as small as possible without perceptibly degrading hearing assistance provided by the hearing protection system100. For example, N may be between 100 and 500 samples.

As noted above, in order to reduce hearing loss, the stapedial reflex is advantageously elicited as soon as possible. Accordingly, bypass facility608may be configured to bypass some or all of the sound processing functionality of the processing facility604used to transmit a drive signal to implantable stimulator106. Bypass facility608may be a software bypass or a hardware bypass. For example, in response to a determination that a level of an audio signal exceeds the predetermined threshold, bypass facility608may generate a drive signal instructing implantable stimulator106to stimulate one or more stimulation sites effective to elicit the stapedial reflex. The drive signal may not relate to the actual output of sound detector102. For example, the drive signal may be a predefined signal or signal generated according to predefined parameters. Inasmuch as the drive signal is not based on the actual output of the sound detector102, functions of the processing facility604may be bypassed, such as one or more pre-processing operations, spectral analysis operations, noise reduction operations, mapping operations, and/or any other types of signal processing operations on a detected audio signal as may serve a particular application.

In some example implementations, bypass facility608includes a separate hardware path from threshold facility606to headpiece202. Accordingly, threshold facility606may utilize the separate hardware path to transmit a drive signal to headpiece202upon detecting exceeding of the threshold by the output of the sound detector102.

FIG. 7illustrates an exemplary implementation700of hearing protection system300wherein implantable stimulator106, intracochlear electrodes206, and stapedial electrode108are implanted within a user.FIG. 7also shows various anatomical features associated with the perception of sound, some of which will now be described in order to facilitate an understanding of the systems and methods described herein.

As shown inFIG. 7, the ear may include a pinna702, ear canal704, tympanic membrane706, malleus708, incus710, stapedius muscle712, stapes714, oval window716, round window718, various structures within the cochlea (e.g., the scala tympani720, the scala vestibuli722, the basilar membrane724, and the helicotrema726), the labyrinth728, and the auditory nerve730. In a normally functioning ear, the tympanic membrane706vibrates in response to ambient sound, and via the ossicular chain (which includes the malleus708, the incus710, and the stapes714), the vibration is transferred to the oval window716. The stapedius muscle712acts as a hearing damper by exerting a force on the stapes714and thereby increasing the impedance of the middle ear when uncomfortable sound levels are detected. The damping caused by contraction of the stapedius muscle712may be on the order of approximately 20 dB.

As shown inFIG. 7, sound processor104may be located external to the user and mounted behind the ear, i.e., pinna702. Headpiece202is positioned such that a coil disposed therein may be inductively coupled to a corresponding coil included within implantable stimulator106. In this manner, sound processor104may transmit control parameters to implantable stimulator106by way of communication link110. Lead204may also be implanted within the user such that electrodes206are disposed within the cochlea. Implantable stimulator106may generate and apply electrical stimulation to one or more stimulation sites within the cochlea via electrodes206. Lead112also extends from implantable stimulator106to stapedial electrode108, which may be secured to, or in otherwise in contact with, the stapedius muscle, the stapedius tendon, and/or an area adjacent either of these members.

FIG. 8shows details of morphology of the stapedius muscle712and shows that a belly802of the stapedius muscle712is surrounded by a bone structure referred to as the pyramidal eminence804. The belly802of the stapedius muscle812is connected to the stapes714by the stapedius tendon806, a portion of which is not surrounded by the pyramidal eminence804.

The stapedial electrode108may secure to or contact one or both of the stapedius tendon806and the belly802of the stapedius muscle712. In some examples, the stapedial electrode108may be embodied as a band or clamp partially or completely encircling the stapedius tendon806. In other examples, the stapedius electrode108is embedded within the belly802of the stapedius muscle. In still other examples, the stapedius electrode108secures to the tissue of the pyramidal eminence804at a location such that current from the stapedial electrode108is effective to stimulate the stapedius muscle712.

FIG. 9illustrates an exemplary method900of eliciting the stapedial reflex of a user using a stapedial electrode. WhileFIG. 9illustrates exemplary steps according to one exemplary implementation, other implementations may omit, add to, reorder, and/or modify any of the steps shown inFIG. 9. One or more of the steps shown inFIG. 9may be performed by a sound processor104and/or any implementation thereof.

At step902, the sound processor104detects a below-SRT signal. A below-SRT signal may be a signal for which the output of the sound detector102is below a predefined threshold that corresponds to a loudness at or below an estimated stapedial reflex threshold (SRT) of humans in general or specific to the user.

At step904, the sound processor104processes the below-SRT signal into drive signals. As discussed above, the drive signals are configured to direct the implantable simulator106to apply stimulation currents to the electrodes206positioned in a cochlea of a user. The drive signals may be based on the amplitude and frequency content of the below-SRT signal such that the stimulation currents are effective to give the user perception of sound corresponding to the below-SRT signal.

At step906, the sound processor104transmits the drive signals corresponding to the below-SRT signal to the implantable stimulator106. As discussed, above, the implantable stimulator then generates stimulation current for the electrodes206positioned in the cochlea of the user according to the drive signals.

At step908, the sound processor104detects an above-SRT signal. An above-SRT signal may be a signal for which the output of the sound detector102is above the predefined threshold of step902or some other threshold that generally corresponds to an estimated SRT of humans in general or the user.

At step910, the sound processor104responds to the above-SRT signal by bypassing signal processing to generate a stapedial electrode signal. The stapedial electrode signal may direct the implantable electrode106to apply stimulation current to the stapedial electrode108. Bypassing signal processing may include bypassing some or all of the steps required to generate drive signals representing the above-SRT signal, such as one or more pre-processing operations, spectral analysis operations, noise reduction operations, mapping operations, and/or any other types of signal processing operations on a detected audio signal as may serve a particular application. As noted above, bypassing may include executing a software bypass whereby code defining some or all of these signal processing function is not executed with respect to the above-SRT signal or is not executed until after the sound processor104has responded to the above-SRT signal. As also noted above, bypassing may include invoking a hardware bypass whereby logic encoding sound processing functionality is bypassed by a separate circuit for responding to above-SRT signals.

At step912, the sound processor104transmits the stapedial electrode signal to the implantable electrode106, which then generates corresponding stimulation current that is applied to the stapedial electrode108. The stimulation current applied to the stapedial electrode may be effective to elicit contraction of the stapedius muscle effective to attenuate vibrations reaching the cochlea of the user (e.g., by at least 20 dB).

As noted above, other exemplary implementations of the method900may omit, add to, reorder, and/or modify any of the steps shown inFIG. 9. For example, where the sound processor104is incorporated into the exemplary implementation of hearing protection system100shown inFIG. 1, e.g. lacking intracochlear electrodes206, steps902-906may be omitted. Likewise, at step910, the sound processor910may generate a stapedial electrode signal without bypassing sound processing logic inasmuch as it may not be present in the sound processor104.

FIG. 10illustrates another exemplary method1000of eliciting the stapedial reflex of a user using a stapedial electrode. WhileFIG. 10illustrates exemplary steps according to one embodiment, other exemplary implementations may omit, add to, reorder, and/or modify any of the steps shown inFIG. 10. One or more of the steps shown inFIG. 10may be performed by a sound processor104and/or any implementation thereof.

The method1000may include detecting, at step1002, a below-SRT signal, processing, at step1004, the below-SRT signal into drive signals, and transmitting, at step1006, the drive signals to the implantable stimulator106in the same manner as for the method900using the sound processor104.

At step1008, the sound processor1004the sound processor104detects an above-SRT signal in the same manner as for the method900.

At step1010, the sound processor104responds to the above-SRT signal by bypassing signal processing to generate a drive signal for high frequency electrodes206of the intracochlear electrodes206positioned in the cochlea of the user. As noted above, in many users with hearing loss, low-frequency hearing may still be present whereas high-frequency hearing is significantly impaired. According, a drive signal generated by the sound processor104in response to the above-SRT signal may direct the implantable stimulator106to only stimulate those electrodes206corresponding to higher frequencies (e.g., above 1000 Hz) and refraining from stimulating those electrodes206corresponding to lower frequencies (e.g., below 1000 Hz). The drive signal generated in response to the above-SRT signal may direct the implantable stimulator106to stimulate the high frequency electrodes206at a level sufficiently high to elicit the user's stapedial reflex, i.e., trigger the user's nervous system to contract the stapedius muscle.

The drive signal generated in response to the above-SRT signal may not be based on actual frequency content and/or amplitude of the above-SRT signal, i.e., the stimulation current generated by the implantable stimulator106in response to the drive signal will not be configured to cause the user to perceive a representation of the actual above-SRT signal, but rather perceive a sound configured to elicit the stapedius reflex of the user. In some embodiments, the drive signal in response to the above-SRT signal may be configured to instruct the implantable stimulator to apply stimulation current to the high-frequency electrodes206at a most comfortable level (“M level”) associated with the user, which may be at SRT level. High-frequency electrodes206may be at least a portion of those electrodes corresponding to frequencies above 1 kHz. In particular, the stimulation current in response to the drive signal may be such that it does not result in damage to the hearing or other tissues of the user. Bypassing signal processing to generate the drive signal in response to the above-SRT signal at step1010may include using a software or hardware bypass in the same manner as for the method900.

At step1012, the sound processor104transmits the drive signal from step1010to the implantable electrode106, which then generates corresponding stimulation current that is applied to the electrodes206, specifically the high-frequency electrodes206. The stimulation current applied to the high-frequency electrodes may be effective to elicit the stapedius reflex of the user effective to attenuate vibrations reaching the cochlea of the user by at least 25 dB.

FIG. 11illustrates an exemplary method1100of eliciting the stapedial reflect of a user. WhileFIG. 11illustrates exemplary steps according to one exemplary implementation, other implementations may omit, add to, reorder, and/or modify any of the steps shown inFIG. 11. One or more of the steps shown inFIG. 11may be performed by sound processor104and/or any implementation thereof.

In step1102, a sound processor receives an audio signal presented to the user and detected by a sound detector. For example, a sound detector102may detect the audio signal and produce an output received by the sound processor104.

In step1104, the sound processor determines whether a level of the audio signal exceeds a predetermined threshold, such as a threshold corresponding to an estimate of the SRT of the user. Step1104may be performed in any of the ways described herein.

In step1106, the sound processor directs the implantable stimulator to elicit the stapedial reflex within the user by applying electrical stimulation to one or more stimulation sites. For example, electrical stimulation may be directed to be applied to a stapedial electrode108or to high frequency electrodes206of an intracochlear electrode array as described hereinabove.