Cochlear Implant Signal Processing for Fine Time Structure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current speech coding strategies for cochlear implants primarily transmit slow-varying signal envelope information, failing to effectively convey fine time structure cues, which are masked by amplitude modulations, and when they do attempt to transmit fine time structure, amplitude modulations from unresolved harmonics interfere and partially mask this information.
Innovation Solution
A method for processing acoustic signals in cochlear implants that involves generating band pass signals for each electrode, determining a sequence signal based on the channel-specific sampling sequence, filtering the envelope to reduce modulations from unresolved harmonics, and weighting the sequence signal with the filtered envelope to enhance the perception of fine time structure, using techniques such as low pass filtering and psychoacoustic masking models.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If current speech coding strategies transmit slow-varying signal envelope information, then speech understanding is improved, but fine time structure cues are lost
Solution Approach 1:
The audio signal is divided into multiple frequency bands using a filter bank, with each band processed independently to extract both envelope and fine time structure cues. This segmentation allows simultaneous transmission of slow-varying envelope information and fast-varying fine structure cues without loss
Solution Approach 2:
The patent transitions from transmitting only one-dimensional envelope information to transmitting both envelope and fine time structure dimensions. By adding the fine time structure dimension through channel-specific sampling sequences, the system captures both slow and fast temporal variations in the audio signal
2Loss of information
If fine time structure is transmitted using channel-specific sampling sequences, then fine time structure perception is improved, but amplitude modulations from unresolved harmonics interfere and mask this information
Solution Approach 1:
The patent extracts and removes unwanted amplitude modulations from the envelope signal using a notch filter tuned to the fundamental frequency. This extraction of harmful components allows the fine time structure information to be transmitted without interference from unresolved harmonic modulations
Solution Approach 2:
The patent converts the harmful amplitude modulations from unresolved harmonics into useful information by using the fundamental frequency notch filter to identify and remove these modulations. The removal process actually enhances the clarity of the fine time structure cues by eliminating the masking effect
Data Source
AI summary
A system and method of signal processing for a hearing implant. The hearing implant includes at least one electrode, each electrode associated with a channel specific sampling sequence. An acoustic audio signal is processed to generate for each electrode a band pass signal representing an associated band of audio frequency. For each electrode, a sequence signal is determined as a function of the electrode's associated band pass signal and channel specific sampling sequence. An envelope of each band pass signal is determined. The envelope of each band pass signal is filtered to reduce modulations resulting from unresolved harmonics, creating for each electrode an associated filtered envelope signal. Each electrode's sequence signal is weighted based, at least in part, on the electrode's associated filtered envelope signal.