Binaural Cochlear Implant Processing

[0001] This application claims priority from U.S. Provisional Patent Application 61/857,756, filed July 24, 2014, which is incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to audio signal processing in cochlear implant systems.

BACKGROUND ART

[0003] A normal ear transmits sounds as shown in Figure 1 through the outer ear 101 to the tympanic membrane (eardrum) 102, which moves the bones of the middle ear 103 (malleus, incus, and stapes) that vibrate the oval window and round window openings of the cochlea 104. The cochlea 104 is a long narrow duct wound spirally about its axis for approximately two and a half turns. It includes an upper channel known as the scala vestibuli and a lower channel known as the scala tympani, which are connected by the cochlear duct. The cochlea 104 forms an upright spiraling cone with a center called the modiolar where the spiral ganglion cells of the acoustic nerve 113 reside. In response to received sounds transmitted by the middle ear 103, the fluid-filled cochlea 104 functions as a transducer to generate electric pulses which are transmitted to the cochlear nerve 113, and ultimately to the brain.

[0004] Hearing is impaired when there are problems in the ability to transduce external sounds into meaningful action potentials along the neural substrate of the cochlea 104. To improve impaired hearing, auditory prostheses have been developed. For example, when the impairment is related to operation of the middle ear 103, a conventional hearing aid may be used to provide acoustic-mechanical stimulation to the auditory system in the form of amplified sound. Or when the impairment is associated with the cochlea 104, a cochlear implant with an implanted stimulation electrode can electrically stimulate auditory nerve tissue with small currents delivered by multiple electrode contacts distributed along the electrode. [0005] Figure 1 also shows some components of a typical cochlear implant system which includes 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 into the implant processor 108. Besides receiving the processed audio information, the implant processor 108 also performs additional signal processing such as error correction, pulse formation, etc., and produces a stimulation pattern (based on the extracted audio information) that is sent through an electrode lead 109 to an implanted electrode array 110. Typically, this electrode array 110 includes multiple electrode contacts 112 on its surface that provide selective stimulation of the cochlea 104.

[0006] The human auditory processing system segregates specific sound objects from complex auditory scenes using several binaural cues such as interaural time and level differences (ITD / ILD) and monaural cues such as harmonicity or common onset. This process is known as auditory scene analysis (ASA) as described more fully in A. S.

Bregman Auditory Scene Analysis: The Perceptual Organization of Sound, MIT Press, Cambridge, Mass (1990), incorporated herein by reference. Hearing impaired patients have difficulties successfully performing such an auditory scene analysis even with a hearing prosthesis such as a cochlear implant. Because of such problems, cochlear implant users often struggle to listen to a single individual sound source within a mixture of multiple sound sources as in a noisy sound environment. In the case of understanding speech, this translates into reduced speech intelligibility. In the case of music, musical perception is degraded due to the inability to successfully isolate and follow individual instruments.

[0007] U.S. Patent Publication 20100135500 describes a binaural hearing system with microphones on either side of the patient's head based on comparing the relative signal-to- noise ratios from each microphone. But there is no suggestion as to analysis and processing of sound objects in the surrounding sound environment. SUMMARY OF THE INVENTION

[0008] Embodiments of the present invention are directed to a cochlear implant system for a patient located in a surrounding sound environment. A first microphone is located on the same side of the patient's head as the ear with the cochlear implant for generating an ipsilateral microphone signal. A second microphone is located on the opposite side of the patient's head as the ear with the cochlear implant for generating a contralateral microphone signal. A sound object identification module processes the ipsilateral microphone signal and the contralateral microphone signal in real time to identify one or more sound objects in the sound environment. A sound object selection module selects for each sound object the microphone signal from the microphone closer to the sound object to determine a corresponding sound object microphone signal. A sound object processor combines and processes the sound object microphone signals to generate one or more stimulation signals to the cochlear implant.

[0009] The sound object processor may combine the sound object microphone signals based on adjusting a phase component and/or an amplitude component of each sound object microphone signal. The sound object selection module may select the microphone closer to the sound object using sound object time difference components and/or sound object amplitude components in the microphone signals. The first and second microphones may be located next to the ear or in the ear canal on each side of the patient's head.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 shows elements of a human ear and cochlear implant system.

[0011] Figure 2 shows various functional blocks in a sound processing arrangement for cochlear implants according to one embodiment of the present invention.

[0012] Figure 3 shows an example situation for a single sound object which is closer to the ipsilateral microphone.

[0013] Figure 4 shows an example situation for two sound objects. DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0014] Embodiments of the present invention are directed to a sound processing arrangement and corresponding method for a hearing impaired listener that performs real time identification, selection and processing of sound objects in the sound environment around the patient user. This produces binaural sound processing with a single cochlear implant that has more accurate timing and level information for the sound objects, thereby providing improved localization and better hearing of sound events.

[0015] Figure 2 shows functional blocks in one embodiment where a first microphone 201 on the same side of the patient's head as the ear with the cochlear implant generates an ipsilateral microphone signal. A second microphone 202 on the opposite side generates a contralateral microphone signal. The first and second microphones 201 and 202 may be located next to the ear or in the ear canal on each side of the patient's head. Typically, each microphone signal may be initially processed by one or more preprocessor modules 203 to initially analyze and adjust the signals.

[0016] A sound object identification module 204 processes the ipsilateral microphone signal and the contralateral microphone signal in real time makes an analysis of the acoustic properties of the sound environment to identify the individual sound objects (SO). For each k ^th identified sound object, the sound object identification module 204 calculates two sound object subsets, SOki and SOkc ·

[0017] A sound object selection module 205 selects for each sound object the microphone signal from the microphone closer to the sound object to determine a corresponding sound object microphone signal. For example, the sound object selection module 205 may use sound object time difference components (i.e., phase difference) and/or sound object amplitude components in the microphone signals to select the microphone closer to a given sound object. If both microphone signals are substantially identical, the microphone closer to a sound object will provide a stronger signal and the signal will arrive earlier, and in this way, the sound object selection module 205 will select the stronger and earlier microphone signal for each sound object as the corresponding sound object microphone signal. For each sound object, the sound object selection module 205 outputs only the selected sound object microphone signal. If the sound object selection module 205 does not identify any sound objects as present, then the sound may be processed from one microphone only, preferably from the ipsilateral microphone 201.

[0018] Figure 3 shows an example situation where a given sound object (SOi) is identified to be closer to the ipsilateral microphone. The sound object selection module 205 in Figure 2 will select only the ipsilateral microphone signal for use as the sound object microphone signal. Figure 4 shows another situation with two different sound objects, one of which (SOi) is closer to the ipsilateral side and the other of which (SO ₂ ) is closer to the contralateral side. The sound object selection module 205 selects only SOH and SO _2C as sound object microphone signals for output.

[0019] A sound object processor 206 includes a sound object summation module 207 that combines the sound object microphone signals from the sound object selection module 205 and a stimulation signal processor 208 that generates one or more stimulation signals to the cochlear implant based on user-specific fitting characteristics. The sound object processor 206 may combine the sound object microphone signals based on adjusting a phase component and/or an amplitude component of each sound object microphone signal.

[0020] The entire system operates in real time so as to correctly track moving sound objects. If the SOi in Fig. 3 were to be moving from left to right, the SOi _c microphone signal will be selected as the SOi sound object microphone signal as soon as SOi is identified to be closer to the contralateral microphone 202. The system components may be encased in a processor housing that may be worn either on the body (e.g., behind the ear) or that may be fully implantable.

[0021] Embodiments of the invention may be implemented in part in any conventional computer programming language. For example, preferred embodiments may be implemented in a procedural programming language (e.g., "C") or an object oriented programming language (e.g., "C++", Python). Alternative embodiments of the invention may be implemented as pre-programmed hardware elements, other related components, or as a combination of hardware and software components.

[0022] Embodiments can be implemented in part as a computer program product for use with a computer system. Such implementation may include a series of computer instructions fixed either on a tangible medium, such as a computer readable medium (e.g., a diskette, CD-ROM, ROM, or fixed disk) or transmittable to a computer system, via a modem or other interface device, such as a communications adapter connected to a network over a medium. The medium may be either a tangible medium (e.g., optical or analog communications lines) or a medium implemented with wireless techniques (e.g., microwave, infrared or other transmission techniques). The series of computer instructions embodies all or part of the functionality previously described herein with respect to the system. Those skilled in the art should appreciate that such computer instructions can be written in a number of programming languages for use with many computer architectures or operating systems. Furthermore, such instructions may be stored in any memory device, such as semiconductor, magnetic, optical or other memory devices, and may be transmitted using any communications technology, such as optical, infrared, microwave, or other transmission technologies. It is expected that such a computer program product may be distributed as a removable medium with accompanying printed or electronic documentation (e.g., shrink wrapped software), preloaded with a computer system (e.g., on system ROM or fixed disk), or distributed from a server or electronic bulletin board over the network (e.g., the Internet or World Wide Web). Of course, some embodiments of the invention may be implemented as a combination of both software (e.g., a computer program product) and hardware. Still other embodiments of the invention are implemented as entirely hardware, or entirely software (e.g., a computer program product).

[0023] Although various exemplary embodiments of the invention have been disclosed, it should be apparent to those skilled in the art that various changes and modifications can be made which will achieve some of the advantages of the invention without departing from the true scope of the invention.