Harmonic-Corrected Frequency Compression for Hearing Aid Audio
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Solution Overview
Problem
Existing frequency compression methods in hearing aids fail to preserve the harmonic structure of audio signals, leading to artifacts and reduced audibility in 'dead regions' of hearing loss, particularly for voiced sounds.
Innovation Solution
A method and device for frequency compression that estimates and maps harmonics from one frequency channel to another, maintaining their integral multiple relationship with the fundamental frequency, thereby reducing artifacts and ensuring harmonics remain intact during compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If frequency compression is applied by simply copying channels from higher frequency to lower frequency, then the frequency components can be shifted into audible ranges, but the harmonic structure of the signal is destroyed and artifacts are generated
Solution Approach 1:
The patent applies parameter changes by calculating a correction factor based on the frequency ratio between source and target channels, then using this factor to adjust the harmonic frequencies. This transforms the simple linear frequency mapping into a non-linear mapping that preserves harmonic relationships, resolving the contradiction between ease of compression and harmonic preservation
Solution Approach 2:
The patent implements feedback by estimating the fundamental frequency from the compressed signal and using this estimation to generate expected harmonic frequencies. The actual harmonic frequencies are then adjusted to match these expected values, creating a feedback loop that ensures harmonic structure is maintained during compression
2Reliability
If amplification is applied to compensate for hearing loss, then audibility is improved in most frequency ranges, but it has no effect or is disadvantageous in dead regions
Solution Approach 1:
The patent uses frequency compression as an intermediary technique that bridges the gap between amplification and hearing loss compensation. By shifting frequencies from dead regions to audible ranges, it enables audibility in cases where direct amplification fails, thus adapting to different types of hearing loss including dead regions
3Ease of operation
If frequency compression is used to shift spectral components from dead regions to audible ranges, then audibility is improved, but artifacts are generated due to destruction of harmonic pattern
Solution Approach 1:
The patent changes the frequency mapping parameter from linear to non-linear by introducing a correction factor that accounts for the harmonic structure. This parameter change allows frequency compression to expand accessibility to audible ranges while minimizing artifact generation through preservation of harmonic relationships
Data Source
AI summary
Artifacts occurring during frequency compression, in particular in the case of hearing aids, are avoided or reduced. The method compresses the frequency of an audio signal having a fundamental frequency and at least one harmonic. The audio signal is provided in a plurality of frequency channels. The harmonic of the audio signal is shifted or mapped from a first frequency channel of the plurality of frequency channels into a second frequency channel. In addition a frequency which is likewise harmonic with respect to the fundamental frequency is estimated in the second frequency channel, the harmonic being shifted or mapped onto the estimated frequency. As a result the harmonic pattern is preserved in the compressed signal and the artifacts are reduced.