Multiphonic pitch enhancement in cochlear implants

Abstract

A cochlear implant system for processing polyphonic pitches includes an electrode array implanted in a patient's cochlea. The electrode array includes a first set of electrodes, wherein each electrode in the first set of electrodes is used to be implanted in a first area of ​​the cochlea. The electrode array also includes a second set of electrodes, wherein each electrode in the second set of electrodes is used to be implanted in a second area of ​​the cochlea. The system also includes a sound processor configured to acquire a sound signal having polyphonic pitches. For each electrode in the first set of electrodes and the second set of electrodes, the sound processor generates at least two different modulation frequency signals from the sound signal, such that each modulation frequency signal corresponds to a different pitch in the sound signal. The sound processor stimulates the electrode by simultaneously applying at least two different modulation frequency signals to the electrode.

Description

[0001] Cross-references

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 894,326, filed on August 30, 2019, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to processing polyphonic pitches via a cochlear implant system. Background Art

[0004] like Figure 1 As shown, a normal ear transmits sound to the eardrum (tympanic membrane) 102 through the outer ear 101, moves the bones (malleus, incus and stapes) of the middle ear 103, and the bones of the middle ear 103 vibrate the oval window and round window openings of the cochlea 104. The cochlea 104 is a narrow tube that is spirally wound around its axis for about two and a half turns. It includes an upper channel called the vestibular scala, an intermediate chamber called the middle scala and a lower channel called the scala tympani, which are connected by the cochlear duct. The cochlea 104 forms an upright spiral cone with its center called the modiolus, in which the spiral ganglion cells of the auditory nerve 113 reside. In response to the received sound transmitted by the middle ear 103, the fluid-filled cochlea 104 acts as a transducer to generate electrical impulses, which are transmitted to the cochlear nerve 113 and ultimately transmitted to the brain.

[0005] Hearing is impaired when there is a problem with the ability of the neural substrate along the cochlea 104 to convert external sounds into meaningful action potentials. To improve impaired hearing, auditory prostheses have been developed. For example, when the damage is related to the operation of the middle ear 103, conventional hearing aids or middle ear implants can be used to provide acoustic-mechanical stimulation to the auditory system in the form of amplified sound. Alternatively, when the damage is related to the cochlea 104, a cochlear implant with an implanted stimulation electrode can electrically stimulate the auditory nerve tissue through a small current delivered by multiple electrode contacts distributed along the electrode.

[0006] Figure 1Also shown are some components of a typical cochlear implant system, including an external microphone that provides an audio signal input to an external signal processor 111, where various signal processing schemes can be implemented. The processed signal is then converted into a digital data format, such as a sequence of data frames, for transmission to an implant receiver 108 via an external transmitting coil 107. In addition to receiving the processed audio information, the implant receiver 108 performs additional signal processing such as error correction, pulse forming, and (based on the extracted audio information) generates a stimulation pattern that is transmitted via electrode leads 109 to an implanted electrode array 110. The electrode array 110 includes a plurality of electrode contacts 112 (also referred to as electrode channels) on its surface that provide selective stimulation of the cochlea 104.

[0007] Each electrode channel is typically associated with a frequency band, and each electrode contact addresses a group of neurons with an electrical stimulation pulse having a charge derived from the instantaneous amplitude of the signal envelope within that frequency band. Current cochlear implant encoding strategies map different audio channels to different locations within the cochlea. Figure 2 An example of signal processing using a cochlear implant stimulation (CIS) stimulation strategy is shown. Figure 2 The top portion of shows the sound pressure characteristics of a spoken "A" ( / ay / ), with a sound level of 67.2 dB. Figure 2 The middle waveform in shows the normal healthy auditory system response. Figure 2 The bottom waveform in shows the neural response of auditory nerve fibers under CIS stimulation.

[0008] Figure 3 Various functional blocks in a signal processing arrangement are shown for generating electrode stimulation signals to electrode contacts in an implanted cochlear implant array according to a typical hearing implant system. A pseudocode example of such an arrangement may be as follows:

[0009] Input signal preprocessing:

[0010] BandPassFilter(input_sound,band_pass_signals)

[0011] Envelope extraction:

[0012] BandPassEnvelope(band_pass_signals,band_pass_envelopes)

[0013] Stimulus timing generation:

[0014] TimingGenerate(band_pass_signals,stim_timing)

[0015] Pulse generation:

[0016] PulseGenerate(band_pass_envelopes,stim_timing,out_pulses)

[0017] Details of such an arrangement will be set forth in the discussion that follows.

[0018] exist Figure 3 In the signal processing arrangement shown, an initial input sound signal is generated by one or more sensor microphones, which can be omnidirectional and / or directional. The preprocessor filter bank 301 preprocesses the input sound signal with a set of multiple parallel bandpass filters (e.g., infinite impulse response (IIR) or finite impulse response (FIR)), each bandpass filter is associated with a specific frequency band of the audio, for example, a filter bank with 12 6th order digital Butterworth bandpass filters of the infinite impulse response (IIR) type is used, so that the acoustic audio signal is filtered into a number of K bandpass signals U1 to U K , where each signal corresponds to the frequency band of a bandpass filter. Each output of a sufficiently narrow CIS bandpass filter for a voiced speech input signal can be roughly considered as a sinusoid at the center frequency of the bandpass filter modulated by the envelope signal. This is also due to the quality factor of the filter (Q≈3). In the case of voiced speech segments, the envelope is approximately periodic and the repetition rate is equal to the pitch frequency. Alternatively, but not limited to, the preprocessor filter bank 301 can be implemented based on the use of a Fast Fourier Transform (FFT) or a Short Time Fourier Transform (STFT).

[0019] Based on the tonal topology of the cochlea, each electrode contact of the tympanic membrane is typically associated with a specific bandpass filter of the preprocessor filter bank 301. The preprocessor filter bank 301 may also perform other initial signal processing functions, such as, but not limited to, automatic gain control (AGC) and / or noise reduction and / or wind noise reduction and / or beamforming and other well-known signal enhancement functions. An example of pseudocode for an infinite impulse response (IIR) filter bank based on a direct form II transposed structure is given by Fontaine et al., "Brian Hears: Online Audory Processing Using Vectorization over Channels," Frontiers in Neuroinformatics, 3011; the entire contents of which are incorporated herein by reference.

[0020] Bandpass signal U1 to U K (which can also be considered as an electrode channel) is output to the stimulation timer 306, which includes an envelope detector 302 and a fine structure detector 303. The envelope detector 302 extracts the characteristic envelope signal output Y1, ..., Y K , which represents the channel-specific bandpass envelope. Available Y k =LP(|U k |) represents envelope extraction, where |.| represents absolute value, and LP(.) represents a low-pass filter; for example, 12 rectifiers and 12 IIR type second-order digital Butterworth low-pass filters are used. Alternatively, if the bandpass signals U1, ..., U are generated by an orthogonal filter k is zero, the envelope detector 302 can extract the Hilbert envelope.

[0021] Optionally, the fine structure detector 303 is used to obtain a smooth and robust estimate of the instantaneous frequency in the signal channel, processing the bandpass signals U1, ..., U k The selected temporal fine structure features of K Bandpass signal U1,...,U k can be assumed to be a real-valued signal, so in the specific case of analyzing an orthogonal filter bank, the fine structure detector 303 only considers U k The fine structure detector 303 is composed of K independent parallel submodules with the same structure.

[0022] Pulse generator 304 applies a patient-specific mapping function—for example, using transient nonlinear compression of the envelope signal (mapping method)—that is tailored to the needs of the individual cochlear implant user during the implant fitting process to achieve a natural loudness increase. Pulse generator 304 can apply a logarithmic function with a shape factor C as the loudness mapping function, which is typically the same across all bandpass analysis channels. In different systems, different specific loudnesses may use mapping functions other than the logarithmic function, apply only one common function to all channels, or apply a separate function to each channel to generate the electrode stimulation signal. The electrode stimulation signal is typically a set of symmetrical, biphasic current pulses. Implant 305 receives the output from pulse generator 304.

[0023] Cochlear implant users often have difficulty with the auditory task of music perception. Most music is polyphonic, consisting of multiple simultaneous pitches. Cochlear implant users lack accurate pitch perception. Consequently, they are unable to perceive the different pitches occurring simultaneously in music, instead perceiving these separate pitches as a single pitch. Current cochlear implants do not account for the potential presence of polyphonic pitches when processing a user's audio information.

[0024] Pitch is the psychophysical correlate of a sound's fundamental frequency, which can be used to rank sounds on a frequency scale from low to high. In a normal-hearing ear, the cochlea 104 uses two basic mechanisms to discriminate and encode pitch. These two mechanisms allow the normal-hearing ear to perceive polyphonic pitch. The first mechanism, called positional pitch, activates the region of the cochlea 104 most responsive to the frequency of the incoming pitch signal. Positional pitch is based on the mechanical properties of the basilar membrane and the tonal topology of the cochlea.

[0025] The basilar membrane is located between the middle order and the tympanic membrane of the cochlea 104. Auditory receptor cells (called hair cells) are arranged along the pitch topology gradient of the cochlea 104 and are activated by simulations from the basilar membrane. The hair cells are organized into three rows of outer hair cells (OHC) and one row of inner hair cells (IHC). The OHC modifies the input signal by enhancing the movement of the basilar membrane. The modified input signal is converted to the IHC, which results in a pulse train that transmits the modified input signal to the brainstem along the auditory nerve. The IHC has a characteristic frequency that is tuned to based on their position on the cochlea 104. High-frequency signals activate the basal region of the cochlea 104, while low-frequency signals activate the top region of the cochlea 104. This position-frequency conversion is generally referred to as the tonotopy of the cochlea. In position pitch, the basilar membrane of the cochlea acts as a frequency analyzer and activates hair cells that are specifically tuned to the frequency of the input pitch signal.

[0026] The second mechanism in a normal hearing ear is called rate pitch, which phase-locks the firing rate of auditory neurons (or auditory nerve fibers) to the frequency of the input pitch signal. Thus, the firing peaks of the auditory neurons correspond to periodic peaks in the amplitude of the input signal. Alternating current receptors on the IHC elements cause periodic increases and decreases in glutamate release from the IHCs, resulting in phase locking to the input signal. The brain combines the firing of auditory neurons caused by the input signal into a pattern similar to the characteristic frequency of the input signal.

[0027] In cochlear implant users, the hair cells of the cochlea 104 may be damaged, thereby impairing the place pitch and rate pitch mechanisms of the cochlea 104. Current cochlear implants do not apply treatment strategies to specifically address the impairment in the place pitch and rate pitch mechanisms of the user. Summary of the Invention

[0028] Various embodiments of the present invention relate to a cochlear implant system for processing polyphonic pitches. The system includes an electrode array implanted in the cochlea of ​​a patient. The electrode array includes a first group of electrodes, each electrode in the first group of electrodes is used to be implanted in a first area of ​​the cochlea. The electrode array also includes a second group of electrodes, each electrode in the second group of electrodes is used to be implanted in a second area of ​​the cochlea. The system also includes a sound processor configured to collect sound signals with polyphonic pitches. For each electrode in the first group of electrodes and the second group of electrodes, the sound processor generates at least two different modulation frequency signals from the sound signal, such that each modulation frequency signal corresponds to a different pitch in the sound signal. The sound processor stimulates the electrodes by simultaneously applying at least two different modulation frequency signals to the electrodes.

[0029] In some embodiments, the sound processor is configured to apply at least two different modulated frequency signals to the electrodes in an interleaved arrangement. In some embodiments, each electrode in the first and second sets of electrodes is configured to be implanted on the cochlea at least at a minimum spatial distance from each other electrode in the first and second sets of electrodes. In exemplary embodiments, the sound processor is configured to generate the modulated frequency signals such that the same ratio exists between the two different modulated frequency signals for a given electrode in the first set of electrodes and the two different modulated frequency signals for a given electrode in the second set of electrodes. In some embodiments, the sound processor is configured to generate: the at least two modulated signals for each electrode in the first set of electrodes as low frequency signals, and the at least two modulated signals for each electrode in the second set of electrodes as high frequency signals, wherein the high frequency signals are at a higher frequency relative to the low frequency signals.

[0030] In an exemplary embodiment, the sound processor is configured to select a fundamental frequency for the modulated signal. The selection by the sound processor includes one or more of the following. The selection may include evaluating the fit of a particular electrode and stimulation rate combination to a range of fundamental frequencies. The evaluation is performed by: (i) varying the particular electrode and stimulation rate combination, and (ii) identifying by the patient the desired combination of electrodes and stimulation rates for perceived harmonics of each fundamental frequency. The selection may include executing a running coding strategy that selects the fundamental frequency by performing an extraction process on the sound signal using periodic analysis. In some exemplary embodiments, the running coding strategy selects the fundamental frequency based on extracting: (i) a plurality of fundamental frequencies in the sound signal, (ii) the frequency value of each fundamental frequency, and (iii) the frequency range of the electrodes.

[0031] In some embodiments, the first set of electrodes is located at a more apical region of the cochlea relative to the second set of electrodes, which is located at a more basal region of the cochlea. In some embodiments, at least one of the first set of electrodes and the second set of electrodes comprises at least two electrodes. In some embodiments, the at least two different modulation frequency signals are fundamental frequencies.

[0032] Various embodiments of the present invention relate to a method for processing polyphonic pitches by a cochlear implant system associated with a patient. The cochlear implant system includes an electrode array comprising a first set of electrodes implanted in a first region of the patient's cochlea and a second set of electrodes for implantation in a second region of the patient's cochlea. The method further includes acquiring a sound signal having polyphonic pitches. For each electrode in the first set of electrodes and the second set of electrodes, the method includes generating at least two different modulation frequency signals from the sound signal. Each modulation frequency signal corresponds to a different pitch in the sound signal. The method further includes stimulating the electrode by simultaneously applying the at least two different modulation frequency signals to the electrode.

[0033] In some embodiments, the method applies at least two different modulation frequency signals to the electrodes in an interleaved arrangement. In some embodiments, each electrode in the first and second sets of electrodes is configured to be implanted on the cochlea at least at a minimum spatial distance from each other electrode in the first and second sets of electrodes. In an exemplary embodiment, the modulation frequency signals are generated such that the same ratio exists between the two different modulation frequency signals for a given electrode in the first set of electrodes and the two different modulation frequency signals for a given electrode in the second set of electrodes. In some embodiments, the at least two modulation signals for each electrode in the first set of electrodes are generated as low frequency signals, and the at least two modulation signals for each electrode in the second set of electrodes are generated as high frequency signals, wherein the high frequency signals are at a higher frequency relative to the low frequency signals.

[0034] In an exemplary embodiment, the method further comprises selecting a fundamental frequency of the modulated signal by one or more of the following. The method may include fitting a frequency relationship to the patient by evaluating a specific electrode and stimulation rate combination for a range of fundamental frequencies. The evaluation is performed by (i) varying the specific electrode and stimulation rate combination, and (ii) identifying, by the patient, combined perceived harmonics of each fundamental frequency. The method further comprises executing a run coding strategy that selects the fundamental frequency by performing an extraction process on the sound signal using periodic analysis. In some exemplary embodiments, the method further comprises defining the fundamental frequency by the run coding strategy based on extracting: (i) a plurality of fundamental frequencies in the sound signal, (ii) a frequency value for each fundamental frequency, and (iii) a frequency range for the electrode.

[0035] In some embodiments, the first set of electrodes is located at a more apical region of the cochlea relative to the second set of electrodes, which is located at a more basal region of the cochlea. In some embodiments, at least one of the first set of electrodes and the second set of electrodes comprises at least two electrodes. In some embodiments, the at least two different modulation frequency signals are fundamental frequencies.

[0036] Embodiments of the present invention relate to a non-transitory, tangible computer program product in a computer-readable medium for processing polyphonic pitches by stimulating electrodes of an electrode array in a cochlear implant system associated with a patient. The electrode array includes a first set of electrodes implanted in a first region of the cochlea and a second set of electrodes implanted in a second region of the cochlea. The product includes program code for acquiring a sound signal having polyphonic pitches. For each electrode in the first set of electrodes and the second set of electrodes, the product includes program code for generating at least two different modulation frequency signals from the sound signal. Each modulation frequency signal corresponds to a different pitch in the sound signal. The product also includes program code for stimulating the electrodes by simultaneously applying at least two different modulation frequencies to the electrodes.

[0037] In some embodiments, the at least two different modulation frequency signals are applied to the electrodes in an interleaved arrangement. In some embodiments, each electrode in the first set of electrodes and the second set of electrodes is configured to be implanted in the cochlea at least at a minimum spatial distance from one another. In an exemplary embodiment, the modulation frequency signals are generated such that the same ratio exists between the two different modulation frequency signals for a given electrode of the first set of electrodes and the two different modulation frequency signals for a given electrode of the second set of electrodes. In some embodiments, the at least two modulation signals for each electrode in the first set of electrodes are generated as low frequency signals, and the at least two modulation signals for each of the second set of electrodes are generated as high frequency signals, wherein the high frequency signals are at a higher frequency relative to the low frequency signals.

[0038] In an exemplary embodiment, the product further comprises program code for selecting a fundamental frequency for the modulated signal. The selection comprises one or more of the following. The selection may comprise an assessment of the fit of a particular electrode and stimulation rate combination to a range of fundamental frequencies. The assessment is performed by: (i) varying the particular electrode and stimulation rate combination, and (ii) identifying, by the patient, combined perceived harmonics of each fundamental frequency. The selection may comprise executing an operational coding strategy that selects the fundamental frequency by performing an extraction process on the sound signal using periodic analysis. In some exemplary embodiments, the product may comprise program code for selecting the fundamental frequency by executing the operational coding strategy based on extracting: (i) a plurality of fundamental frequencies in the sound signal, (ii) a frequency value of each fundamental frequency, and (iii) a frequency range of the electrode.

[0039] In some embodiments, the first set of electrodes is located at a more apical region of the cochlea relative to the second set of electrodes, which is located at a more basal region of the cochlea. In some embodiments, at least one of the first set of electrodes and the second set of electrodes comprises at least two electrodes. In some embodiments, the at least two different modulation frequency signals are fundamental frequencies. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The above-described features of the embodiments will be more readily understood by referring to the following detailed description taken in conjunction with the accompanying drawings, in which:

[0041] Figure 1 The anatomy of a typical human ear with a cochlear implant system is shown;

[0042] Figure 2 An example of signal processing using a cochlear implant stimulation strategy is shown;

[0043] Figure 3 shows various functional blocks in a signal processing arrangement for a typical cochlear implant system;

[0044] Figure 4 A block diagram of a cochlear implant fitting system according to an embodiment of the present invention is shown;

[0045] Figure 5 shows various logical steps in the fitting process according to an embodiment of the present invention;

[0046] Figure 6 shows various functional blocks in a signal processing arrangement for a cochlear implant system according to an embodiment of the present invention;

[0047] Figure 7 Shows the various logical steps in the polyphonic pitch encoding process according to an embodiment of the present invention;

[0048] Figure 8 Shows the use of Figure 7Examples of signal processing for cochlear implant stimulation strategies;

[0049] Figure 9 1 and 2. Various logical steps in a polyphonic pitch encoding process of at least two modulated signals on a first set of electrodes and a second set of electrodes, the second set of electrodes being located in a more basal region of the cochlea relative to the first set of electrodes, according to an embodiment of the present invention are shown. DETAILED DESCRIPTION

[0050] Embodiments of the present invention relate to strategies for encoding the polyphonic pitch of an input audio signal in stimulation of electrodes of an implanted electrode array of a cochlear implant system. These embodiments select the fundamental pitch frequency from the input audio signal based on a patient-specific mapping of electrodes to stimulation rates. These embodiments adjust the stimulation rate of the electrodes in the patient-specific mapping by simultaneously modulating the amplitude of the pulsed current on the electrodes with different sinusoidal amplitude modulation frequencies in an interleaved arrangement.

[0051] Figure 4 A block diagram of a cochlear implant fitting system according to an embodiment of the present invention is shown. A control unit 401 for recording and stimulation, such as a Med-El Maestro Cochlear Implant (CI) system, generates stimulation signals and analyzes response measurements. Connected to the control unit 401 is an interface box 402, such as a diagnostic interface system typically used with the Maestro CI system, such as the DIB II, which formats and distributes input and output signals between the control unit 401 and the system components implanted in the patient 406. For example, Figure 4 As shown, there can be an interface lead 403 having one end connected to an interface box 402 and the other end having an electrode plug 407, which then branches out to a cochlear implant electrode array 405 (and an optional extra-cochlear ground electrode 404). For a range of fundamental frequencies (F0), a control unit 401 is configured to match the electrodes of the cochlear implant electrode array 405 to a stimulation rate that provides the most harmonious sound perception for the subject patient. The control unit 401 includes a fitting processor having at least one hardware implant processor device and is controlled by software instructions to perform a fitting process that includes delivering a test stimulation sequence to the electrodes at a stimulation rate that varies over time. The control unit 401 is coupled to a database 410 for storing the results of the fitting process.

[0052] More specifically, the operation Figure 4 The fitting system shown in , so that Figure 5The basic logical steps shown in the method iteratively fit electrodes to the stimulation rate of each fundamental frequency in a set of fundamental frequencies. First, in step 501, a set of fundamental frequencies is selected from a range of fundamental frequencies specific to the subject patient (e.g., 100-600 Hz). Next, for each fundamental frequency in the set, in step 502, a set of electrodes is iteratively fitted. For example, the set of electrodes can be all or part of the electrodes starting sequentially from, for example, the top of the electrode array and working backward along the length of the electrode array. Alternatively, the electrode set can be all or part of the electrodes fitted in a non-linear order along the electrode array. Alternatively, the electrode set can be an alternating sequence of every other electrode contact along at least a portion of the length of the electrode array.

[0053] For each fitting electrode, iteratively, step 503, delivers a fitting stimulation signal to the fitting electrode at a varying stimulation rate, step 504. Step 505 obtains a response to the fitting stimulation signal from the subject patient at the varying stimulation rate, which response may include subjective and / or objective response measurements. For example, the subject patient may scale the perceived pleasantness or harmonicity of the sound from the fitting stimulation signal at each varying rate. Steps 503-505 are performed for each fitting electrode.

[0054] Based on the subject patient's response, step 506 defines a patient-specific fitting map for one or more fitting electrode and stimulation rate combinations for the fundamental frequency. For example, the patient-specific fitting map may define one or more fitting electrode and stimulation rate combinations that provide the subject patient with the most harmonious sound perception at the fundamental frequency. Steps 502-506 are performed for each fundamental frequency in the selected set of fundamental frequencies. The method ends at step 507.

[0055] Figure 6 Various functional blocks in a signal processing arrangement for a cochlear implant system according to an embodiment of the present invention are shown. Figure 6 It is used to process multi-tone audio signals Figure 3 The control unit 601 for fundamental frequency selection is added to the signal processing arrangement to extract and select the fundamental frequency group of the pitch from the input multi-tone audio signal. The control unit 601 retrieves the patient-specific electrode / rate mapping of the fundamental frequency from the database 606 and selects the fundamental frequency group based on the patient-specific mapping. In an embodiment, the method of using Figure 4 Cochlear Implant Fitting System and Figure 5 Methods to generate patient-specific electrode / rate maps.

[0056] A control unit 603 for adjusting the stimulation rate is added to a signal processing arrangement that is coupled to the control unit 601 and the database 606. The control unit 603 receives a selected set of fundamental frequencies from the control unit 601. The control unit 603 adjusts the stimulation rate of certain electrodes of the implanted electrode array 605 over time according to the patient-specific mapping to enhance the selected fundamental frequencies. In particular, a rate pitch perception can be generated at the pulse generator 604 by modulating the amplitude of the current pulses to specific electrodes according to the corresponding stimulation rate in the mapping. An amplitude-modulated rate pitch perception can also be generated when the envelope detector 602 extracts the envelope of the signal and maps the envelope to the corresponding electrodes.

[0057] More specifically, in Figure 7 Following the basic logical steps shown in the method, the operation Figure 6 , a fitting system shown in is used to encode a set of fundamental frequencies from a polyphonic audio signal. First, in step 701, a set of fundamental frequencies is selected from the input polyphonic audio signal. Step 701 can extract relevant information from the audio signal, including the number of fundamental frequencies in the signal, the value of each fundamental frequency, and the frequency range in which each fundamental frequency is located. This extraction can be performed by using a periodicity analyzer that applies methods such as autocorrelation and cepstrum analysis. Step 701 can also retrieve a patient-specific electrode to stimulation rate mapping for the fundamental frequencies. Based on this information, step 701 selects a set of fundamental frequencies from the patient-specific signal. Step 701 can select a set of fundamental frequencies so that the corresponding patient-specific mapping includes specific positions of electrodes on the top region and base region of the cochlea. In addition, a set of fundamental frequencies can be selected so that the corresponding patient-specific mapping includes base region electrodes and top region electrodes placed at a minimum spatial distance from other electrodes implanted on the cochlea.

[0058] Next, step 702, for each fundamental frequency in the group, in step 703, an electrode and stimulation rate map is applied for the fundamental frequency. In particular, step 703 enhances the fundamental frequency at the electrode in the map according to the stimulation rate in the map. To increase the fundamental frequency, step 704 produces a rate pitch sensation according to the fundamental frequency by modulating the amplitude of the pulse current (pulse train) on the electrode with a sine wave of the modulating frequency. The pulse rate of the pulse train is called the carrier rate. This type of pitch encoding that produces temporal pitch is called "sine amplitude modulation". By using a high rate carrier pulse train, step 704 can provide polyphonic pitch cues to convey the pitch sensation at the electrode. Steps 702-704 are performed for each selected fundamental frequency.

[0059] To generate polyphonic pitch cues, for example, sinusoidal amplitude modulation (SAM) can be applied to the electrode's carrier pulse train using the following formula: SAM(t) = f(t) + d × sin(2πfm × t + 3π / 2), where f(t) is the unmodulated pulse train occurring at a threshold level at, for example, 5000 pps, and d is the depth of the modulation. The factor Fm is the modulation frequency and can have a starting phase of 3π / 2. The maximum and minimum values ​​of SAM correspond to the subject's maximum comfort level and the threshold level measured for the unmodulated pulse train.

[0060] Polyphonic pitches can be generated by simultaneously modulating the amplitudes of the pulsed currents on the mapped electrodes corresponding to a selected fundamental frequency with the same sinusoidal amplitude modulation frequency. The polyphonic pitches become stronger as the distance between the electrodes increases. Polyphonic rate pitches are generated by simultaneously modulating the amplitudes of the pulsed currents on the mapped electrodes with different sinusoidal amplitude modulation frequencies. To do this, the carrier rate on the electrodes must be increased to, for example, 10,000 pps, and then modulated current pulses per carrier, for example, 5,000 pps, are presented interleaved across the electrodes. The polyphonic position pitches become stronger as the difference between the different sinusoidal amplitude modulation frequencies increases. In an exemplary embodiment, step 704 generates the sinusoidal amplitude modulation frequencies such that the same ratio exists between the different modulation frequencies for a given top region electrode and the different modulation frequencies for a given base region electrode. In some embodiments, step 704 generates the amplitude modulation frequencies for the top electrode as a low-frequency signal and the amplitude modulation frequencies for the base electrode as a high-frequency signal.

[0061] Step 705 interleaves the different amplitude modulation signals generated for a given electrode. Step 706 applies the amplitude modulation signal to the current pulses of each electrode simultaneously.

[0062] Figure 8 Shows the use of Figure 7 Examples of signal processing for cochlear implant stimulation strategies. Figure 8 At the top, for the electrode 801 on the base region, signal processing generates two different sinusoidal amplitude modulation frequencies 802, 803, which are interleaved and applied to the current pulses of the electrode 801. Figure 8 For the electrode 804 on the top region, signal processing generates two different sinusoidal amplitude modulation frequencies 805, 806, which are interleaved and applied to the current pulses of the electrode 804.

[0063] More specifically, Figure 8 The signal processing shown is in accordance with Figure 9The basic logical steps shown in the method are performed. Step 902 acquires an input sound signal having polyphonic pitches. Based on the stimulation rate mapping of the patient-specific electrodes and fundamental frequencies, a pitch fundamental frequency group is selected from the polyphonic sound signal. In order to produce a polyphonic pitch perception from the sound signal, step 904 selects the fundamental frequencies so that they are mapped to a first group of electrodes on a first region of the cochlea and a second group of electrodes on a second region of the cochlea. In some embodiments, the first group of electrodes can be located in a more top region of the cochlea relative to the second group of electrodes, which is located in a more base region of the cochlea. In some embodiments, one or both of the first group of electrodes and the second group of electrodes may include at least two electrodes.

[0064] For each electrode mapped, step 906 generates a signal to simultaneously modulate the pulse current on the electrode using at least two different sinusoidal amplitude modulation frequencies. For each electrode, step 908 interleaves the at least two different amplitude modulation signals generated for the electrode. For each electrode, step 910 stimulates the electrode by applying the interleaved amplitude modulation signals to the electrode.

[0065] Various embodiments of the present invention are characterized by the potential claims listed in the paragraphs following this paragraph (and before the actual claims provided at the end of this application). These potential claims form part of the written description of this application. Therefore, in subsequent proceedings involving this application or any application claiming priority based on this application, the subject matter of the following potential claims may be filed as actual claims. The inclusion of such potential claims should not be interpreted as meaning that the actual claims do not cover the subject matter of the potential claims. Therefore, a decision not to file these potential claims in subsequent proceedings should not be interpreted as contributing this subject matter to the public.

[0066] The embodiments of the present invention described above are merely exemplary; many variations and modifications will be apparent to those skilled in the art. All such variations and modifications are intended to fall within the scope of the present invention as defined by any of the appended claims.

Claims

1. A cochlear implant system for processing polyphonic pitches, characterized in that: The system comprises: An electrode array implanted in the cochlea of ​​a patient, the electrode array comprising: a first set of electrodes, each electrode in the first set of electrodes being adapted to be implanted in a first region of the cochlea, and a second set of electrodes, each electrode in the second set of electrodes being adapted for implantation in a second region of the cochlea; and A sound processor, the sound processor being configured to: collecting a sound signal having polyphonic pitches; and For each electrode in the first set of electrodes and the second set of electrodes: generating at least two different modulation frequency signals from the sound signal, each modulation frequency signal corresponding to a different pitch in the sound signal, and stimulating the electrode by simultaneously applying the at least two different modulation frequency signals to the electrode, wherein the sound processor is configured to apply the at least two different modulation frequency signals to the electrodes in an interleaved arrangement, or Wherein the sound processor is configured to generate the modulation frequency signals such that there is a same ratio between the two different modulation frequency signals for a given electrode in the first set of electrodes and the two different modulation frequency signals for a given electrode in the second set of electrodes.

2. The system according to claim 1, wherein: Each electrode of the first and second sets of electrodes is configured to be implanted on the cochlea at least at a minimum spatial distance from each other electrode of the first and second sets of electrodes.

3. The system according to claim 1, wherein: The sound processor is configured to generate: at least two modulated signals for each electrode in the first set of electrodes as low frequency signals, and at least two modulated signals for each electrode in the second set of electrodes as high frequency signals, wherein the high frequency signals are at a higher frequency relative to the low frequency signals.

4. The system according to claim 3, characterized in that The sound processor is configured to select a fundamental frequency for the modulated signal, wherein the selecting comprises one or more of: evaluating the fit of electrode and stimulation rate combinations for a range of fundamental frequencies by (i) varying the electrode and stimulation rate combinations and (ii) identifying by the patient a desired combination of electrode and stimulation rate for each perceived harmonic of the fundamental frequency; and A running coding strategy is executed that selects the fundamental frequency by performing an extraction process on the sound signal using periodic analysis.

5. The system according to claim 4, characterized in that The operational encoding strategy selects the fundamental frequency based on extracting: (i) a plurality of fundamental frequencies in the sound signal, (ii) a frequency value of each fundamental frequency, and (iii) a frequency range of the electrode.

6. The system according to claim 3, wherein: The first set of electrodes is located in a more apical region of the cochlea relative to the second set of electrodes, which is located in a more basal region of the cochlea.

7. The system according to claim 1, wherein: At least one of the first group of electrodes and the second group of electrodes includes at least two electrodes.

8. The system according to claim 1, wherein: The at least two different modulation frequency signals are fundamental frequencies.

9. A non-transitory tangible computer program product in a computer-readable medium, characterized in that For processing polyphonic pitches by stimulating electrodes of an electrode array in a cochlear implant system associated with a patient, the electrode array comprising a first set of electrodes implanted in a first region of the cochlea and a second set of electrodes implanted in a second region of the cochlea, the product comprising: Program code for acquiring a sound signal having polyphonic pitches; and For each electrode in the first set of electrodes and the second set of electrodes: program code for generating at least two different modulation frequency signals from the sound signal, each modulation frequency signal corresponding to a different pitch in the sound signal; and program code for stimulating the electrode by simultaneously applying the at least two different modulation frequencies to the electrode, wherein the at least two different modulation frequency signals are applied to the electrodes in an interleaved manner, or Wherein, the modulation frequency signals are generated such that the same ratio exists between two different modulation frequency signals for a given electrode in the first group of electrodes and two different modulation frequency signals for a given electrode in the second group of electrodes.

10. The product according to claim 9, characterized in that Each electrode of the first and second sets of electrodes is configured to be implanted on the cochlea at least at a minimum spatial distance from each other electrode of the first and second sets of electrodes.

11. The product according to claim 9, characterized in that At least two modulation signals for each electrode in the first set of electrodes are generated as low frequency signals, and at least two modulation signals for each electrode in the second set of electrodes are generated as high frequency signals, wherein the high frequency signals are at a higher frequency relative to the low frequency signals.

12. The product according to claim 11, characterized in that Also included is program code for selecting the modulating signal for a base frequency, wherein the selecting comprises one or more of: performing fit assessments for electrode and stimulation rate combinations across a range of fundamental frequencies by: (i) varying the electrode and stimulation rate combinations, and (ii) identifying, by the patient, combined perceived harmonics of each fundamental frequency; and A running coding strategy is executed that selects the fundamental frequency by performing an extraction process on the sound signal using periodic analysis.

13. The product according to claim 12, characterized in that The product also includes program code for selecting the fundamental frequency by executing a coding strategy based on extracting: (i) a plurality of fundamental frequencies in the sound signal, (ii) a frequency value of each fundamental frequency, and (iii) a frequency range of the electrode.

14. The product according to claim 11, characterized in that The first set of electrodes is located in a more apical region of the cochlea relative to the second set of electrodes, which is located in a more basal region of the cochlea.

15. The product according to claim 9, characterized in that At least one of the first set of electrodes and the second set of electrodes includes at least two electrodes.

16. The product according to claim 9, characterized in that The at least two different modulation frequency signals are fundamental frequencies.

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