Broadband Low-Frequency Filter for Cochlear Implant Temporal Resolution
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Solution Overview
Problem
Cochlear implant systems face limitations in temporal resolution and channel interaction, leading to distortions and unintended hearing impressions due to spatial channel interaction, particularly in representing temporal fine structure information across neighboring electrodes.
Innovation Solution
A cochlear implant system utilizing a broadband low-frequency filter associated with a stimulation electrode, processing acoustic signals to generate broadband signals covering 100 Hz to 1000 Hz, which are used to stimulate electrodes with sign-correlated pulses, minimizing channel interaction by positioning electrodes at specific distances and using algorithms like Channel Interaction Compensation and Selected Group to avoid distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple electrodes are stimulated simultaneously with high stimulation rates, then temporal resolution is improved, but spatial channel interaction causes distortion and unintended hearing impressions
Solution Approach 1:
The patent segments the audio frequency spectrum into multiple frequency channels, each processed independently through separate filter banks. This allows temporal fine structure information to be preserved in specific frequency ranges while avoiding interaction between different spatial channels, thus resolving the contradiction between high temporal resolution and channel interaction distortion
Solution Approach 2:
The patent transitions from spatial channel separation to frequency-based channel separation by processing signals through multiple frequency-specific filter banks. This dimensional change allows simultaneous stimulation of multiple electrodes without spatial channel interaction, as each electrode receives stimulation based on its specific frequency channel's temporal fine structure
2Loss of information
If broadband low frequency signals are applied to multiple electrodes, then temporal fine structure representation is improved, but channel interaction causes distortion
Solution Approach 1:
The patent applies local quality by assigning different signal processing characteristics to different frequency channels. Specifically, temporal fine structure information is extracted and preserved only in low-frequency channels (below 1000 Hz) where it is most relevant, while high-frequency channels use different processing. This localized approach improves temporal fine structure representation without causing distortion across all channels
Solution Approach 2:
The patent segments the frequency spectrum into distinct channels with specific processing rules. Low-frequency channels receive broadband signals with temporal fine structure preservation, while high-frequency channels receive different processing. This segmentation allows temporal fine structure to be represented where needed without causing channel interaction distortion in other frequency ranges
Data Source
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Figure 3A~3C
AI summary
A system and method of generating electrode stimulation signals for an implanted multi-channel electrode array of a cochlear implant includes processing an acoustic audio signal with a bank of filters. Each filter in the bank of filters is associated with at least one channel having an electrode. The bank of filters includes a first band pass filter that produces a broadband signal b(t) with frequencies that substantially cover at least one of a pitch frequency range of 100 Hz to 400 Hz and a first format range of 400 Hz - 1000 Hz. At least one electrode associated with the first band pass filter is activated with electrode stimulation signals based, at least in part, on the broadband signal b(t). The filter bank may include at least one electrode associated with one or more filters other than the first band pass filter, the one or more filters producing signals having only higher frequencies than broadband signal b(t).