Frequency Transposition Hearing Aid Envelope Phase Separation
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Solution Overview
Problem
Conventional hearing aids struggle to compensate for hearing impairments, particularly at certain frequencies due to feedback oscillation issues and 'dead regions' where hearing ability is severely degraded, leading to limitations in sound quality and speech intelligibility.
Innovation Solution
The method involves transposing the envelope information of higher frequency source bands into lower frequency target bands while maintaining the phase information, allowing for improved sound quality and speech intelligibility by selectively compressing or expanding frequency ranges based on the user's hearing ability and the type of input signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional amplification is used to compensate for hearing impairment at certain frequencies, then the amplification gain can be increased, but feedback oscillation occurs and sound quality deteriorates
Solution Approach 1:
The patent introduces frequency transposition as an intermediary mechanism that converts high-frequency signals to low-frequency signals through a third processing stage, avoiding direct amplification at problematic frequencies. The transposition process acts as a mediator that preserves speech intelligibility while eliminating feedback oscillation issues by routing signals through a different frequency pathway.
Solution Approach 2:
The patent changes the frequency parameter of the signal by transposing high-frequency components to low-frequency regions. This parameter transformation allows the system to overcome amplification limitations at specific frequencies by redistributing spectral energy to frequencies where the hearing aid can provide stable gain without feedback.
2Power
If amplification is increased to compensate for dead regions, then the hearing threshold can be overcome, but the basilar membrane cannot process the amplified signals effectively
Solution Approach 1:
Frequency transposition serves as an intermediary that bypasses dead regions by mapping frequencies from damaged areas to functional areas of the basilar membrane. Instead of attempting to stimulate non-functional sensory cells directly, the system transposes the information to frequency regions where sensory cells are still operational, maintaining effective stimulus transmission.
Solution Approach 2:
The patent inverts the conventional approach by not trying to amplify signals at dead region frequencies, but rather by taking signals from those frequencies and relocating them to frequencies where the auditory system remains functional. This inverse strategy of mapping from damaged to undamaged regions overcomes the limitation of non-functional sensory cells.
3Loss of information
If frequency transposition is applied to improve speech intelligibility, then audibility at inaudible frequencies is improved, but phase relationship may be distorted affecting sound quality
Solution Approach 1:
The patent extracts the envelope information from the high-frequency signal and separately processes it through transposition, while preserving the phase characteristics. By separating the amplitude envelope from the phase information and handling them differently, the system maintains speech intelligibility through envelope transposition while preserving natural sound quality through phase relationship maintenance.
Solution Approach 2:
The patent applies different processing qualities to different aspects of the signal: the envelope undergoes frequency transposition to improve audibility, while the phase information is preserved with minimal alteration to maintain sound quality. This localized differential processing ensures that each component receives the appropriate treatment for its specific function.
4Adaptability or versatility
If the entire frequency range is compressed to fit residual hearing area, then coverage of audible frequencies is improved, but the complexity of the compression scheme increases
Solution Approach 1:
The patent segments the frequency spectrum into distinct bands and applies different transposition strategies to each band based on the user's hearing profile. Rather than compressing the entire frequency range uniformly, the system divides frequencies into regions that can be processed independently, allowing for customized compression ratios and target frequency assignments for each segment, thereby reducing overall system complexity.
Solution Approach 2:
The patent implements dynamic frequency transposition where the compression ratio and target frequencies are adjusted based on the input signal characteristics and user needs. The system can adaptively change processing parameters in real-time, applying aggressive compression only where necessary while maintaining natural frequency relationships in other regions, thus balancing coverage with processing simplicity.
Data Source
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Figure 2a~2c
Figure 3a
AI summary
The application relates to a method of improving a user's perception of an input sound. The application further relates to an audio processing device and to its use. The object of the present application is to increase the sound quality of a sound signal as perceived by a user, e.g. a hearing impaired user. The method comprises a) Defining a critical frequency fcrit between a low frequency range and a high frequency range; b) Analyzing an input sound in a number of frequency bands below and above said critical frequency; c) Defining a cut-off frequency fcut below said critical frequency fcrit; d) Identifying a source frequency band above said cut-off frequency fcut; e) Extracting the envelope of said source band; f) Identifying a corresponding target band below said critical frequency fcrit; g) Extracting the phase of said target band; h) Combining the envelope of said source band with the phase of said target band. This has the advantage of increasing the sound quality, and the potential to further improve speech intelligibility in frequency transposition, e.g. frequency lowering systems. The invention may e.g. be used in communication devices, such as telephones, or listening devices, e.g. hearing instruments, headsets, head phones, active ear protection devices or combinations thereof.