Cochlear Implant Temporal Fine Structure Encoding
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Solution Overview
Problem
Cochlear implants struggle with pitch detection and sound source localization due to their inability to replicate the temporal fine structure of sound, leading to adaptation and reduced information transfer, especially in noisy environments.
Innovation Solution
A system and method for cochlear implants that involves band-pass filtering and applying a Hilbert transform to input audio signals to identify positive-moving zero crossings, triggering electric current pulses timed to occur near the maxima of the audio waveform, thereby minimizing adaptation and enhancing the use of monaural and binaural cues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If constant rate electric pulses are delivered to the electrode, then the device structure is simple and easy to manufacture, but the nervous system adapts to the repetitive periodic signal and ignores the stimulation, reducing information transfer
Solution Approach 1:
The patent applies periodic action by delivering electric pulses at a constant rate (e.g., 900 pulses per second) to stimulate the auditory nerve. This periodic stimulation pattern is designed to replicate the temporal fine structure of natural sounds, creating a rhythmic activation pattern that prevents neural adaptation while maintaining information transfer efficiency.
Solution Approach 2:
The patent changes the parameter of pulse delivery from conventional envelope-based modulation to direct temporal fine structure encoding. By preserving the instantaneous amplitude and phase information of the acoustic signal and mapping it to pulse timing and amplitude, the system transforms how information is encoded, thereby preventing adaptation and improving information transfer to the nervous system.
2Device complexity
If temporal fine structure is not preserved in the stimulation signal, then the device processing is simpler, but users cannot segregate target sounds from background maskers in noisy environments
Solution Approach 1:
The patent extracts the temporal fine structure components from the acoustic signal by analyzing the instantaneous amplitude and phase information. This extraction process isolates the critical temporal features needed for sound segregation, separating them from the envelope information, and uses only these extracted features for neural stimulation, thereby enabling sound segregation without excessive processing complexity.
Solution Approach 2:
The patent introduces an intermediary processing stage that transforms acoustic signal characteristics into neural stimulation parameters. This intermediary layer maps the temporal fine structure of acoustic signals to the timing and amplitude of electric pulses, serving as a bridge between acoustic reality and neural perception, thereby enabling reliable sound segregation in noisy environments.
3Ease of operation
If electric pulses are delivered at constant rate, then the device operation is simple, but pitch detection and sound source localization abilities are reduced
Solution Approach 1:
The patent performs preliminary analysis of the acoustic signal to extract temporal fine structure characteristics before generating the stimulation pattern. By pre-processing the acoustic signal to identify instantaneous amplitude and phase information, the system prepares the appropriate stimulation parameters in advance, enabling accurate pitch detection and sound localization while maintaining simple constant-rate pulse delivery operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves pitch detection, sound source localization, and reduces the negative effects of adaptation, allowing for better utilization of binaural cues and improved sound segregation in noisy environments by encoding the temporal fine structure of the input audio signal.
Implementation Method 1
apply a Hilbert transform to at least one of the plurality of channel signals to generate a transformed audio signal
Data Source
AI summary
A hearing assistance device and method is presented. An electrode is configured to be disposed within a cochlea of a user. A processor is in communication with the electrode and is configured to stimulate the electrode. The processor is configured to receive an input audio signal, band-pass filter the input audio signal into a plurality of channel signals, apply a Hilbert transform to at least one of the plurality of channel signals to generate a transformed audio signal, and analyze the transformed audio signal to identify at least one positive-moving zero crossing of the transformed audio signal. Upon identifying the at least one positive-moving zero crossing of the transformed audio signal, the processor is configured to trigger an electric current pulse to be delivered to the electrode.