Binaural Cochlear Implant Interaural Time Difference Encoding
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Solution Overview
Problem
Cochlear implant systems fail to effectively encode interaural time difference (ITD) cues, making it difficult for patients to spatially locate sound sources and distinguish between sounds and noise, as existing systems often encode ITD cues inappropriately or at high stimulation pulse rates that are not perceivable by patients.
Innovation Solution
A binaural cochlear implant system that uses microphones at each ear to detect audio signals, process fine structure information, and generate timing pulse signals to represent ITD cues, allowing for accurate perception of spatial sound locations by applying electrical stimulation at a low and optimized pulse rate based on fine structure information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ITD cues are encoded at high stimulation pulse rates to reproduce sound content accurately, then sound content fidelity is improved, but ITD perception becomes difficult for patients
Solution Approach 1:
The patent segments the stimulation signal into two distinct components: fine structure information (carrying sound content) delivered at high pulse rates, and envelope information (carrying ITD cues) delivered at lower pulse rates. This segmentation allows each component to be optimized independently for its respective function.
Solution Approach 2:
The patent employs periodic modulation of the stimulation pulse rates, varying the pulse rate according to the envelope of the audio signal. This periodic variation encodes ITD information in the timing patterns of stimulation pulses while maintaining the overall high pulse rate needed for sound content fidelity.
2Ease of manufacture
If ITD cues are encoded with timing unrelated to the sound being represented, then encoding simplicity is improved, but ITD naturalness and perception become worsened
Solution Approach 1:
The patent extracts fine structure information from the audio signal before generating the stimulation pattern. This preliminary extraction of temporal cues from the actual sound waveform ensures that subsequent ITD encoding is naturally synchronized with the sound being represented, improving both naturalness and patient perception.
Solution Approach 2:
The system uses the envelope of the audio signal as feedback to dynamically adjust the timing and rate of stimulation pulses. This feedback mechanism ensures that ITD cues are continuously synchronized with the incoming sound, maintaining naturalness while allowing for flexible encoding strategies.
Data Source
AI summary
A binaural cochlear implant system (system) includes first and second microphones associated with first and second ears of a patient, respectively. The microphones detect an audio signal presented to the patient and output first and second signals representative of the audio signal as detected at the first and second ears, respectively. The system also includes a first sound processor that receives the first signal from the first microphone and the second signal from a second sound processor by way of a communiation link with the second sound processors. The first sound processor generates first and second fine structure signals representative of fine structure information of the first and second fine structure signals, respectively, and generates a timing pulse signal based on the first and second fine structure signals. The first sound processor uses the timing pulse signal to represent to the patient an interaural time difference between the first and second signals.