Phase Triggered Envelope Sampler for Cochlear Implants
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Solution Overview
Problem
Cochlear implant users experience significant performance degradation in noisy environments and struggle to enjoy music due to limitations in pitch perception and transmission of fine time structure information.
Innovation Solution
A coding strategy for cochlear implants that combines noise-robust envelope sampling with fine time structure processing, using phase-dependent signal limiting periods to ensure that the fine structure rate remains below the pitch rate perceptual limit, allowing for accurate pitch discrimination and improved music enjoyment by correlating signal limiting periods with the phase of band pass signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the stimulation rate is increased to transmit fine time structure information, then pitch discrimination improves, but the system becomes vulnerable to noise and loses robustness
Solution Approach 1:
The audio signal is divided into multiple frequency bands using bandpass filters, with each band processed independently. This segmentation allows the system to transmit fine time structure information at higher rates for pitch discrimination while maintaining noise robustness through selective processing of different frequency components
Solution Approach 2:
The system dynamically adjusts the sampling rate and stimulation parameters based on the phase information of the audio signal. By changing the sampling rate according to the instantaneous frequency and phase, the system optimizes both pitch discrimination and noise robustness across different acoustic conditions
2Reliability
If envelope sampling is used to improve noise robustness, then performance in noisy conditions improves, but fine time structure information is lost and pitch discrimination deteriorates
Solution Approach 1:
The system merges envelope sampling techniques with fine time structure processing by combining envelope information from multiple frequency bands with phase information from zero-crossing detection. This fusion allows simultaneous achievement of noise robustness and pitch discrimination capability
Solution Approach 2:
The system adds the dimension of phase information to the traditional envelope-based CIS approach. By incorporating phase data from bandpass filtered signals and using phase-dependent sampling, the system transcends the limitations of one-dimensional envelope processing and achieves enhanced pitch discrimination while maintaining noise robustness
3Use of energy by moving object
If stimulation rate is reduced on basal channels to conserve power, then power consumption decreases, but the ability to transmit fine time structure information is compromised
Solution Approach 1:
The system uses dynamic, phase-dependent sampling rates that adapt to the instantaneous frequency and phase of the audio signal. This dynamic adjustment allows the system to optimize power consumption by reducing the sampling rate when fine time structure information is less critical, while maintaining the ability to transmit fine time structure information when needed
Solution Approach 2:
The system changes the sampling rate parameter based on the phase information and frequency content of the audio signal. By adjusting the sampling rate as a function of phase and frequency, the system optimizes the balance between power consumption and fine time structure transmission across different operational conditions
Data Source
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AI summary
A method of generating electrode stimulation signals for an implanted electrode array is described. An acoustic audio signal is processed to generate band pass signals which each represent an associated band of audio frequencies. For each band pass signal, fine time structure information is extracted to determine a sequence of phase event signals. For each sequence of phase event signals, when the number of phase event signals reaches a channel pitch rate factor, a signal limiting period without signals is introduced to produce a modified sequence of phase event signals. Each modified sequence of phase event signals is weighted with a channel amplitude value in order to generate a set of electrode stimulation signals for the implanted electrode array.