(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2003/0215105 A1
`Sacha
`(43) Pub. Date:
`NOV. 20, 2003
`
`US 20030215105A1
`
`(54) HEARING AID WITH TIME-VARYING
`PERFORMANCE
`
`(52) U.S. Cl.
`
`......................... .. 381/312; 381/314; 381/316
`
`(76)
`
`Inventor: Mike K. Sacha, Chanhassen, MN (US)
`
`Correspondence Address:
`Schwegman, Lundberg, Woessner & Kluth, P.A.
`P.0. Box 2938
`
`57
`
`)
`
`(
`
`ABSTRACT
`
`Minneapolis: MN 55402 (US)
`
`Ahearing aid that compensates for a patient’s hearing deficit
`
`(21) Appl. No‘:
`
`10/146,986
`
`(22)
`
`Ffled3
`
`May 15: 2002
`Publication Classification
`
`51
`
`Int. Cl.7 ................................................... .. H04R 25/00
`
`in a gradually progressing fashion. The hearing aid may be
`programmed to successively select in a defined sequence a
`parameter set that defines at least one operating character-
`istic of the signal processing circuit from a group of such
`parameter sets. The defined sequence may end in a param-
`P
`Y
`P
`P
`g
`eter set that o timall
`com ensates the
`atient‘s hearin .
`
`1 00
`
`112
`
`Input
`Transducer
`
`1.1.9
`
`
`
`
`Processor
`E-Q
`
`Memory
`
`
`
`Gain Control
`
`Filtering/Amp
`1_2Q
`
`
`
`@
`Noise Reduction
`Audio Amp
`135
`150
`
`
`
`
`
`
`
` Programming
`Interface
`
`2.12
`
`
`Output
`Transducer
`All
`
`
`HIMPP 1004
`
`HIMPP 1004
`
`

`

`Patent Application Publication Nov. 20, 2003 Sheet 1 of 2
`
`US 2003/0215105 A1
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`US 2003/0215105 A1
`
`Nov. 20, 2003
`
`HEARING AID WITH TIME-VARYING
`PERFORMANCE
`
`FIELD OF THE INVENTION
`
`[0001] This invention pertains to devices and methods for
`treating hearing disorders and, in particular, to electronic
`hearing aids.
`
`BACKGROUND
`
`[0002] Hearing aids are electronic instruments worn in or
`around the ear that compensate for hearing losses by ampli-
`fying sound. Because hearing loss in most patients occurs
`non-uniformly over the audio frequency range, most com-
`monly in the high frequency range, hearing aids are usually
`designed to compensate for the hearing deficit by amplifying
`received sound in a frequency—specific manner. Adjusting a
`hearing aid’s frequency specific amplification characteristics
`to achieve a desired optimal target response for an individual
`patient is referred to as fitting the hearing aid. The optimal
`target response of the hearing aid is determined by testing
`the patient with a series of audio tones at dilferent frequen-
`cies. The volume of each tone is then adjusted to a threshold
`level at which it is barely perceived by the patient. The
`hearing deficit at each tested frequency can be quantified in
`terms of the gain required to bring the patients hearing
`threshold to a normal value. For example, if the normal
`hearing threshold for a particular frequency is 40 dB, and the
`patient’s hearing threshold is 47 dB, 7 dB of amplification
`gain by the hearing aid at that frequency results in optimal
`compensation.
`
`[0003] Most often, a new hearing aid user is not fitted with
`the optimal target response at the first audiologist visit. This
`is because a patient with a hearing deficit that is suddenly
`compensated at an optimal level may find the new sounds
`uncomfortable or even intolerable until adaptation occurs.
`Patients initially fitted with optimal compensation may even
`discontinue using their hearing aid. Therefore, it is common
`practice for the audiologist to initially fit the hearing aid with
`a sub-optimal degree of compensation which is then ramped
`up to the optimal level during subsequent fittings at a rate the
`patient finds comfortable.
`
`SUMMARY
`
`[0004] Adjusting a hearing aid with repeated fittings per-
`formed by an audiologist, however, may be inconvenient
`and also adds to the expense of the device for the patient. In
`accordance with the present invention, a hearing aid is
`equipped with a signal processing circuit for filtering and
`amplifying an input signal
`in accordance with a set of
`specified signal processing parameters that dictate the fil-
`tering and amplification characteristics of the device. The
`parameter set may also define other operating characteristics
`such as the degree of compression or noise reduction. The
`hearing aid is then programmed to automatically sequence
`through different parameter sets so that its compensation
`gradually adjusts from a sub-optimal to an optimal level.
`The device may be programmed to select a signal processing
`parameter set for specifying to the signal processing circuit
`from a group of such parameter sets in a defined sequence
`based upon elapsed operating time intervals as measured by
`a timer or upon a specified number of detected power events
`representing the device being turned on.
`
`BRIEF DJ:lSCRII"I‘ION OF THE DRAWINGS
`
`[0005] FIG. 1 is a block diagram of the components of an
`exemplary hearing aid.
`
`[0006] FIG. 2 illustrates a particular implementation of
`circuitry for automatic selection of signal processing param-
`eters.
`
`DETAILED DESCRIPTION
`
`[0007] A hearing aid is a wearable electronic device for
`correcting hearing loss by amplifying sound. The electronic
`circuitry of the device is contained within a housing that is
`commonly either placed in the external ear canal or behind
`the ear. Transducers for converting sound to an electrical
`signal and vice-versa may be integrated into the housing or
`external
`to it. The basic components of an exemplary
`hearing aid are shown in FIG. 1. A microphone or other
`input transducer 110 receives sound waves from the envi-
`ronment and converts the sound into an input signal IS. After
`amplification by pre-amplifier 112, the signal IS is sampled
`and digitized by AH) converter 114. Other embodiments
`may incorporate an input transducer that produces a digital
`output directly. The device’s signal processing circuitry 100
`processes the digitized input signal IS into an output signal
`OS in a manner that compensates for the patient’s hearing
`deficit. The output signal OS is then passed to an audio
`amplifier 150 that drives an output
`transducer 160 for
`converting the output signal into an audio output, such as a
`speaker within an earphone.
`
`In the embodiment illustrated in FIG. 1, the signal
`[0008]
`processing circuitry 100 includes a programmable controller
`made up of a processor 140 and associated memory 220 for
`storing executable code and data. The overall operation of
`the device is determined by the programming of the con-
`troller, which programming may be modified via a program-
`ming interface 210. The programming interface 210 allows
`user input of data to a parameter modifying area of the
`memory 220 so that parameters alfecting device operation
`may be changed. The programming interface 210 may allow
`communication with a variety of devices for configuring the
`hearing aid such as industry standard programmers, wireless
`devices, or belt-worn appliances.
`
`[0009] The signal processing modules 120, 130, and 135
`may represent specific code executed by the controller or
`may represent additional hardware components. The filter-
`ing and amplifying module 120 amplifies the input signal in
`a frequency specific manner as defined by one or more signal
`processing parameters specified by the controller. As
`described above, the patient’s hearing deficit is compensated
`by selectively amplifying those frequencies at which the
`patient has a below normal hearing threshold. Other signal
`processing functions may also be performed in particular
`embodiments. The embodiment illustrated in FIG. 1, for
`example, also includes a gain control module 130 and a
`noise reduction module 135. The gain control module 130
`dynamically adjusts the amplification in accordance with the
`amplitude of the input signal. Compression, for example, is
`a form of automatic gain control that decreases the gain of
`the filtering and amplifying circuit to prevent signal distor-
`tion at high input signal levels and improves the clarity of
`sound perceived by the patient. Other gain control circuits
`may perform other functions such as controlling gain in a
`frequency specific manner. The noise reduction module 135
`
`

`

`US 2003/0215105 A1
`
`Nov. 20, 2003
`
`performs functions such as suppression of ambient back-
`ground noise and feedback cancellation.
`
`[0010] The signal processing circuitry 100 may be imple-
`mented in a variety of different ways, such as with an
`integrated digital signal processor or with a mixture of
`discrete analog and digital components. For example, the
`signal processing may be performed by a mixture of analog
`and digital components having inputs that are controllable
`by the controller that define how the input signal is pro-
`cessed, or the signal processing functions may be imple-
`mented solely as code executed by the controller. The terms
`“controller,”“module,” or “circuitry” as used herein should
`therefore be taken to encompass either discrete circuit
`elements or a processor executing programmed instructions
`contained in a processor-readable storage medium.
`
`[0011] The programmable controller specifies one or more
`signal processing parameters to the filtering and amplifying
`module and/or other signal processing modules that deter-
`mine the manner in which the input signal IS is converted
`into the output signal OS. The one or more signal processing
`parameters that define a particular mode of operation are
`referred to herein as a signal processing parameter set. A
`signal processing parameter set
`thus defines at least one
`operative characteristic of the hearing aid’s signal process-
`ing circuit. Aparticular signal processing parameter set may,
`for example, define the frequency response of the filtering
`and amplifying circuit and define the manner in which
`amplification is performed by the device. In a hearing aid
`with more sophisticated signal processing capabilities, such
`as for noise reduction or processing multi—channel inputs,
`the parameter set may also define the manner in which those
`functions are performed.
`
`[0012] As noted above, a hearing aid programmed with a
`parameter set that provides optimal compensation may not
`be initially well tolerated by the patient. In order to provide
`for a gradual adjustment period,
`the controller is pro-
`grammed to select a parameter set from a group of such sets
`in a defined sequence such that the hearing aid progressively
`adjusts from a sub-optimal to an optimal level of compen-
`sation delivered to the patient. In order to define the group
`of parameter sets,
`the patient is tested to determine an
`optimal signal processing parameter set that compensates for
`the patient’s hearing deficit. From that information, a sub-
`optimal parameter set that is initially more comfortable for
`the patient can also determined, as can a group of such sets
`that gradually increase the degree of compensation. The
`controller of the hearing aid is then programmed to select a
`signal processing parameter set for use by the signal pro-
`cessing circuitry by sequencing through the group of signal
`processing parameter sets over time so that the patient’s
`hearing is gradually compensated at increasingly optimal
`levels until the optimal signal processing parameter set is
`reached. For example, each parameter set may include one
`or more frequency response parameters that define the
`amplification gain of the signal processing circuit at a
`particular frequency. In one embodiment, the overall gain of
`the hearing aid is gradually increased with each successively
`selected signal processing parameter set. If the patient has a
`high frequency hearing deficit, the group of parameter sets
`may be defined so that sequencing through them results in a
`gradual increase in the high frequency gain of the hearing
`aid. Conversely, if the patient has a low frequency hearing
`deficit, the hearing aid may be programmed to gradually
`
`increase the low frequency gain with each successively
`selected parameter set. In this manner, the patient is allowed
`to adapt
`to the previously unheard sounds through the
`automatic operation of the hearing aid. Other features imple-
`mented by the hearing aid in delivering optimal compensa-
`tion may also be automatically adjusted toward the optimal
`level with successively selected parameter sets such as
`compression parameters that define the amplification gain of
`the signal processing circuit at a particular input signal level,
`parameters defining frequency specific compression, noise
`reduction parameters, and parameters related to multi—chan-
`nel processing.
`[0013] FIG. 2 illustrates how a scheme for altering the
`performance of a hearing aid over time as described above
`may be implemented in the programmable controller. The
`controller includes a flash memory 220 that retains its
`contents when the device is powered down. Also, other types
`of memory may be used such as SRAM (Static Random
`Access Memory) in combination with Lithium Polymer
`batteries. The programming interface 210 represents a com-
`munications channel by which the device may be configured
`with variable operating parameters that are stored in the
`flash memory 220. One such parameter is an enable function
`for an event register 240 that, when enabled, records a power
`event input representing the powering up of the hearing aid.
`The output of the event register 240 toggles an input to an
`event counter 250 to count the number of power up cycles.
`The contents of the event counter 250 is stored in the flash
`memory when the device is powered down and restored
`from the flash memory when the device is powered up so
`that a running tally of the number of power up cycles can be
`maintained. When the event counter counts a specified
`number of power up cycles, the counter is cleared and one
`or more address pointers 260 are incremented. The specified
`number of power up cycles counted by the event counter
`before it is cleared is communicated via the programming
`interface and stored in the flash memory. The address pointer
`or pointers 260 are stored in the flash memory when the
`device is powered down and point to a signal processing
`parameter set that
`is then used by the signal processing
`circuit
`to process received sound. The signal processing
`parameter sets are stored in one or more tables 270 that are
`contained in either the flash memory or other storage
`medium. In the example shown, a parameter set consists of
`M parameters, and a separate table is provided for each
`parameter. Each of the M parameter tables contains N
`alternative parameter values that can be included in the set.
`The tables thus collectively contain a group of N different
`parameter sets that can be selected for use by the hearing aid.
`The controller can then be programmed to sequence through
`the group of parameter sets from an initial parameter set to
`a final parameter set.
`[0014]
`In an exemplary mode of operation, a user defines
`the N parameter sets so that each set represents a progressive
`increase in the degree of hearing compensation. The device
`is then configured to initially use parameter set #1 by
`specifying the address pointers 260 to point to parameter #1
`in each of the parameter tables 270. Parameter set #1 may
`represent a sub-optimal degree of hearing compensation that
`the patient finds comfortable. The user also specifies a
`particular number of power up events before the device
`switches to the next parameter set. When the event counter
`250 counts that number of power up events, the address
`pointers 260 are incremented to point to the next parameter
`
`

`

`US 2003/0215105 A1
`
`Nov. 20, 2003
`
`set. This process continues until the address pointers point to
`parameter set #N, which may represent optimal hearing
`compensation for the patient.
`
`In an alternative embodiment, a timer 230 is pro-
`[0015]
`vided that operates when the device is powered on. The
`timer records the time during which the device is powered
`up and stores that value in the flash memory when the device
`is powered down. A running total of the operating time for
`the device can thus be maintained. Rather than basing the
`sequencing through the signal processing parameter sets on
`the number of power up events as described above,
`the
`device may successively select a new parameter set after a
`specified operating time interval has elapsed. The progres-
`sion from each parameter set to another may occur after the
`same operating time interval, or different operating time
`intervals may be defined for each parameter set.
`
`[0016] Although the invention has been described in con-
`junction with the foregoing specific embodiments, many
`alternatives, variations, and modifications will be apparent
`to those of ordinary skill in the art. Other such alternatives,
`variations, and modifications are intended to fall within the
`scope of the following appended claims.
`
`What is claimed is:
`
`1. A hearing aid, comprising:
`
`an input transducer for converting sound into an input
`signal;
`
`a signal processing circuit for filtering and amplifying the
`input signal in accordance with a set of specified signal
`processing parameters to thereby produce an output
`signal;
`
`an output transducer for converting the output signal into
`sound;
`
`for specifying processing
`a programmable controller
`parameters to the signal processing circuit; and,
`
`wherein the controller is programmed to select a signal
`processing parameter set for specifying to the signal
`processing circuit from a group of such parameter so
`that the performance of the hearing aid varies over
`time.
`
`2. The hearing aid of claim 1 wherein the controller is
`programmed to sequence through the group of parameter
`sets from an initial parameter set to a final parameter set.
`3. The hearing aid of claim 2 wherein the final parameter
`set is designed to optimally compensate for a particular
`patient’s hearing deficit.
`4. The hearing aid of claim 1 further comprising a timer
`and wherein the controller is programmed to sequence
`through the group of parameter sets in accordance with
`elapsed operating time intervals.
`5. The hearing aid of claim 4 wherein the timer is
`operative only when the hearing aid is powered up and
`further comprising a flash memory for storing operating time
`intervals.
`
`6. The hearing aid of claim 5 wherein the controller is
`programmed to select a next parameter set from the group of
`parameter sets after a specified operating time interval.
`7. The hearing aid of claim 5 wherein the controller is
`programmed to select a next parameter set from the group of
`parameter sets after an operating time interval specified for
`each parameter set.
`
`8. The hearing aid of claim 1 further comprising a power
`event detector and wherein the controller is programmed to
`sequence through the group of parameter sets in accordance
`with detected power events that represent powering up of the
`hearing aid.
`9. The hearing aid of claim 5 further comprising a power
`event counter and wherein the controller is programmed to
`sequence through the group of parameter sets in accordance
`with a specified number of counted power events.
`10. The hearing aid of claim 1 wherein the controller is
`programmed to sequence through the group of parameter
`sets by incrementing a pointer stored in memory that indexes
`into one or more tables containing the group of parameter
`sets.
`
`11. The hearing aid of claim 1 wherein each parameter set
`includes one or more frequency response parameters that
`define the amplification gain of the signal processing circuit
`at a particular frequency.
`12. The hearing aid of claim 1 wherein each parameter set
`includes one or more gain control parameters that define
`how the gain of the signal processing circuit is adjusted at a
`particular input signal level.
`13. The hearing aid of claim 1 wherein each parameter set
`includes one or more noise reduction parameters that define
`how the signal processing circuit reduces noise in the input
`signal.
`14. A method for operating a hearing aid, comprising:
`
`converting sound into an input signal;
`
`filtering and amplifying the input signal in accordance
`with a set of specified signal processing parameters to
`thereby produce an output signal;
`
`converting the output signal into sound;
`
`specifying signal processing parameters by selecting a
`signal processing parameter set from a group of such
`parameter sets so that the performance of the hearing
`aid varies over time.
`
`15. The method of claim 14 further comprising sequenc-
`ing through the group of parameter sets from an initial
`parameter set to a final parameter set.
`16. The method of claim 15 wherein the final parameter
`set is designed to optimally compensate for a particular
`patient’s hearing deficit.
`17. The method of claim l4 further comprising sequenc-
`ing through the group of parameter sets in accordance with
`elapsed operating time intervals.
`18. The method of claim 17 wherein operating time
`intervals are recorded only when the hearing aid is powered
`up and further comprising storing operating time intervals in
`a flash memory.
`19. The method of claim 17 further comprising selecting
`a next parameter set from the group of parameter sets after
`a specified operating time interval.
`20. The method of claim 17 further comprising selecting
`a next parameter set from the group of parameter sets after
`an operating time interval specified for each parameter set.
`21. The method of claim 14 further comprising sequenc-
`ing through the group of parameter sets in accordance with
`detected power events that represent powering up of the
`hearing aid.
`22. The method of claim 14 further comprising sequenc-
`ing through the group of parameter sets by incrementing a
`
`

`

`US 2003/0215105 A1
`
`Nov. 20, 2003
`
`pointer stored in memory that indexes into one or more
`tables containing the group of parameter sets.
`23. The method of claim 14 wherein each parameter set
`includes one or more frequency response parameters that
`define the amplification gain of the signal processing circuit
`at a particular frequency.
`24. The method of claim 14 wherein each parameter set
`includes one or more compression parameters that define the
`amplification gain of the signal processing circuit at a
`particular input signal level.
`25. A method for fitting a hearing aid to a patient,
`comprising:
`
`testing the patient to determine an optimal signal process-
`ing parameter set that compensates for the patient’s
`
`hearing deficit, Where a signal processing parameter set
`defines at
`least one operative characteristic of the
`hearing aid’s signal processing circuit; and,
`
`programming the hearing aid to select a signal processing
`parameter set for use by the signal processing circuitry
`by sequencing through a group of signal processing
`parameter sets over time so that the patient’s hearing is
`gradually compensated at increasingly optimal levels
`until the optimal signal processing parameter set
`is
`reached.
`
`