Cochlear Implant Interaural Time Difference Enhancement
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Solution Overview
Problem
Current cochlear implants limit the use of interaural timing cues for sound source localization and speech unmasking in individuals with residual hearing in one ear, as they do not effectively account for the time difference in sound arrival between ears, particularly in cases where one ear is fitted with a hearing aid or no device is attached.
Innovation Solution
A bilateral hearing system that includes a cochlear implant with a filter bank to obtain band-pass filtered signals, a time selector to determine inflection points in the sound signal, a modulator to apply delayed electrical stimulation based on these inflections, and electrodes to deliver the stimulation, synchronized with the auditory nerve stimulation in the opposite ear to maintain interaural timing cues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cochlear implant delivers electrical stimulation to the auditory nerve, then hearing sensation is induced in the implant recipient, but interaural timing cues for sound source localization and speech unmasking are not effectively preserved
Solution Approach 1:
The system performs preliminary analysis of the sound signal to detect inflection points (peaks or valleys) before generating electrical stimulation pulses. By identifying these temporal features in advance and using them to trigger stimulation at precisely timed moments, the system preserves interaural timing relationships while delivering effective auditory nerve stimulation.
Solution Approach 2:
The system incorporates a feedback mechanism where the detected inflection points from the sound signal directly control the timing of electrical stimulation pulses. This closed-loop approach ensures that stimulation timing accurately reflects the temporal structure of the acoustic signal, thereby preserving interaural timing cues for sound localization and speech unmasking.
2Speed
If electrical stimulation is delivered immediately upon receiving sound signal, then response time is minimized, but interaural time difference perception is degraded
Solution Approach 1:
The system performs preliminary detection of inflection points in the sound signal before generating stimulation pulses. This allows the system to maintain minimal processing delay while ensuring that stimulation timing accurately reflects the temporal structure of the acoustic signal, thereby preserving interaural time difference perception.
3Adaptability or versatility
If a bilateral hearing system is implemented with different devices in each ear, then residual hearing is preserved in one ear, but synchronization of auditory nerve stimulation between ears is compromised
Solution Approach 1:
The cochlear implant system uses feedback from detected sound signal inflection points to control stimulation timing. By using the same temporal reference (inflection points) that the hearing aid in the other ear uses for acoustic stimulation, the system achieves synchronization between the two ears despite using different stimulation modalities (electrical vs. acoustic).
Data Source
AI summary
Aspects of the present invention are generally directed to a modulation enhancement strategy that helps improve ITD perception by explicitly modulating the electrical stimulation signal. In an embodiment, the timing of the applied modulations is based on amplitude inflections (i.e., peaks or troughs) in the received sound signal. In an embodiment, the identified inflections (i.e., peaks or troughs) represent the most energetic portions of the signal over a particular time period (e.g., the time period prior to the inflection having a length equal to the expected fundamental period of the signal. Further, in an embodiment, the cochlear implant applies a delay to the stimulation signal to help maintain interaural timing cues. The application of this delay helps account for the traveling wave delay in the acoustic path of the opposite ear in embodiments in which the opposite ear is fitted with a hearing aid or is not fitted with a hearing device.