Hearing Aid Frequency Shift for Comb Filter Suppression
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Solution Overview
Problem
Hearing aids often produce comb filter effects due to the superimposition of environmental sound signals with output sound signals, causing unpleasant changes in overtone spectra and harmonic structures, which existing methods fail to adequately address without impairing user-specific signal processing.
Innovation Solution
A method for operating a hearing aid that classifies the hearing situation and determines parameters like tonality, loudness, stationarity, and reverberation time to apply frequency distortion, specifically frequency shifts, to decorrelate the output signal from environmental sound, thereby suppressing comb filter effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the hearing aid processes the input signal with frequency band filtering and amplification, then the audiological requirements of the user are met, but comb filter effects occur due to time delay between environmental sound and output sound
Solution Approach 1:
The patent applies frequency shifting as a parameter change to the output signal. By shifting the frequency of the processed signal, the time delay-induced phase relationship between environmental sound and output sound is altered, thereby suppressing comb filter effects while preserving the necessary audiological processing quality
Solution Approach 2:
The patent converts the harmful time delay effect into a beneficial frequency shift. Instead of trying to eliminate the time delay completely, the invention uses frequency shifting to transform the harmful interference pattern into a less perceptible form, turning the comb filter problem into an acceptable solution
2Ease of operation
If the hearing aid does not completely shut the auditory canal, then occlusion effects are avoided, but environmental sound superimposes on the output sound causing comb filter effects
Solution Approach 1:
The patent changes the frequency parameter of the output signal to prevent constructive and destructive interference patterns. By applying frequency shifting, the system maintains the open auditory canal configuration (avoiding occlusion effects) while eliminating the harmful superimposition effects through parameter modification
3Object-affected harmful factors
If frequency distortion is applied to suppress comb filter effects, then the phase relation between heterodyne signals is broken, but user-specific signal processing may be impaired
Solution Approach 1:
The patent applies frequency shifting locally to specific frequency bands rather than uniformly across all frequencies. This localized approach allows suppression of comb filter effects in problematic frequency ranges while preserving the integrity of user-specific signal processing in other frequency regions
Solution Approach 2:
The patent applies partial frequency shifting only where necessary to suppress comb filter effects. By using moderate frequency shifts rather than extreme transformations, the system achieves sufficient suppression of harmful effects while maintaining the overall quality and integrity of the user-specific audio processing
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 effectively reduces comb filter effects by breaking the fixed phase relation between heterodyne signals, improving the hearing experience by minimizing destructive interferences and maintaining user-specific signal processing integrity.
Implementation Method 1
A frequency distortion is applied to the first intermediate signal in dependence on the classification of the hearing situation and in dependence on at least one of the four parameters
Implementation Method 2
an input signal is generated by at least one input transducer from a sound signal of the environment
Implementation Method 3
The processed signal is converted by an output transducer into an output sound signal
Implementation Method 4
the output sound signal which has been generated in the hearing aid from the output signal of the signal processing becoming heterodyned with the sound signal of the environment
Implementation Method 5
individual signal components are interfered constructively in dependence on the time delay and frequency which leads to an amplification whereas for frequencies which are a half-integral multiple of the inverse time delay a considerable weakening in the total sound signal can occur due to a destructive interference
Data Source
AI summary
A method operates a hearing aid which has at least one input transducer and at least one output transducer. An input signal is generated by the at least one input transducer from a sound signal in the environment. From the input signal, a classification of a hearing situation of the environment is determined and/or at least one of four parameters including tonality, loudness, stationarity and reverberation time is determined for the sound signal of the environment. A first intermediate signal is generated in dependence on the input signal by signal processing. Wherein by the classification of the hearing situation and by at least one of the four parameters of tonality, loudness, stationarity and reverberation time, at least one parameter of a frequency distortion is predetermined. The frequency distortion predetermined in this way is applied to the first intermediate signal.