Hearing Aid Frequency Transposition for Speech Intelligibility
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Solution Overview
Problem
Current hearing aids fail to effectively convey high-frequency sounds to individuals with steeply sloping sensorineural hearing losses, leading to difficulties in perceiving important sounds like speech, alarms, and environmental noises, as existing transposition algorithms do not accurately maintain harmonic relationships and often deteriorate speech intelligibility.
Innovation Solution
A hearing aid with a signal processor that includes a frequency tracker and a speech detector, which independently transposes selected frequency bands to maintain harmonic relationships and differentiate between voiced and unvoiced speech, ensuring that only unvoiced speech signals are transposed to enhance perception without compromising speech intelligibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequency transposition is applied to convey high-frequency sounds to hearing-impaired users, then perception of important sounds is improved, but speech intelligibility deteriorates due to loss of harmonic relationships
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the transposition ratio based on the detected fundamental frequency. The system calculates the relationship between the fundamental frequency and dominant frequencies to determine optimal transposition parameters, thereby maintaining harmonic relationships while enabling perception of high-frequency sounds.
Solution Approach 2:
The patent implements feedback through continuous tracking of dominant frequencies and fundamental frequencies. The system uses this feedback to adaptively adjust the transposition process, ensuring that harmonic relationships are preserved while conveying high-frequency information to hearing-impaired users.
2Adaptability or versatility
If transposition algorithms are used to shift high-frequency bands to lower bands, then high-frequency perception is enabled, but harmonic relationships are not maintained leading to poor speech quality
Solution Approach 1:
The patent applies dynamics by making the transposition process adaptive rather than fixed. The system continuously tracks the fundamental frequency and adjusts the transposition ratio dynamically to maintain accurate harmonic relationships, thereby preserving speech quality while enabling high-frequency perception.
Solution Approach 2:
The patent segments the frequency spectrum into different bands (high-frequency band, mid-frequency band, low-frequency band) and applies selective transposition to specific bands. This segmentation allows the system to maintain harmonic relationships in speech-critical bands while enabling perception in high-frequency bands.
3Reliability
If all frequency bands are transposed to improve speech perception, then overall sound perception is enhanced, but voiced speech intelligibility is compromised
Solution Approach 1:
The patent applies local quality by differentiating between voiced and unvoiced speech segments and applying transposition selectively. The system maintains the original high-frequency content for voiced speech to preserve intelligibility, while applying transposition primarily to unvoiced segments and environmental sounds, thereby enhancing overall perception without compromising speech quality.
Data Source
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AI summary
A hearing aid comprising a frequency shifter (20) has means (22) for detecting a first frequency and a second frequency in an input signal. The frequency shifter (20) transposes a first frequency range of the input signal to a second frequency range of the input signal based on the presence of a fixed relationship between the first and the second detected frequency. The means (34, 35, 36) for detecting the fixed relationship between the first and the second frequency is used for controlling the frequency transposer (20). A speech detector (26) configured for detecting the presence of voiced and unvoiced speech is provided for suppressing the transposition of voiced-speech signals in order to preserve the speech formants. The purpose of transposing frequency bands in this way in a hearing aid is to render inaudible frequencies audible to a user of the hearing aid while maintaining the original envelope, harmonic coherence and speech intelligibility of the signal. The invention further provides a method for shifting a frequency range of an input signal in a hearing aid.