Hearing Aid Adaptive Noise Reduction via Modulation Detection
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Solution Overview
Problem
Hearing aids struggle to differentiate between modulated and unmodulated sounds at low to medium levels, leading to overamplification of soft sounds and excessive background noise, which interferes with speech clarity.
Innovation Solution
A hearing aid method that splits input signals into frequency bands, calculates noise and absolute average levels, and applies dynamic compression based on amplitude modulation to distinguish and amplify modulated sounds while dampening unmodulated sounds below a certain level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If long attack and release times are used in compressors to keep steady noises below the hearing threshold, then steady environmental noises are suppressed, but faster sudden sounds and modulated sounds like speech are also kept below the threshold and not reproduced
Solution Approach 1:
The patent applies dynamics by making the compression characteristics adjustable and adaptive. The system dynamically switches between different compression settings (long attack/release times for noise suppression, short attack/release times for modulated sounds) based on real-time detection of sound modulation. This resolves the contradiction by allowing the compressor to adapt its behavior to the specific acoustic situation rather than using fixed parameters.
Solution Approach 2:
The patent changes the parameters of the compressor (attack time, release time, compression threshold) based on the detected modulation characteristics of the input signal. When modulated sounds are detected, the system adjusts parameters to allow fast compression; when steady noise is detected, parameters are adjusted for noise suppression. This parameter adaptation resolves the contradiction between noise suppression and modulated sound reproduction.
2Reliability
If shorter attack and release times are used in compressors to reproduce modulated sounds, then speech and sudden sounds are reproduced better, but steady unmodulated noises such as ventilators and traffic noise are amplified excessively
Solution Approach 1:
The system dynamically adjusts compression parameters based on real-time modulation detection. When modulated sounds are present, short attack/release times are applied; when steady noise dominates, long attack/release times are applied. This dynamic adaptation resolves the contradiction by allowing optimal parameters for each sound type without manual intervention.
Solution Approach 2:
The patent implements feedback through modulation detection that continuously monitors the input signal characteristics and adjusts compression parameters accordingly. The system uses the detected modulation level as feedback to control the compressor settings, ensuring that short attack/release times are only used when modulated sounds are present, thus avoiding amplification of steady noise.
3Measurement precision
If a low compression threshold is employed to amplify soft speech sounds, then speech detection is improved, but background noise is also amplified and becomes too loud in relation to speech
Solution Approach 1:
The patent applies local quality by using different compression thresholds for different frequency bands. The system analyzes modulation characteristics in each frequency band separately and applies appropriate compression settings locally. This allows low compression thresholds to be applied selectively to frequency bands containing speech while maintaining higher thresholds in bands dominated by noise, resolving the contradiction between speech detection and noise amplification.
Solution Approach 2:
The system changes compression parameters (threshold, ratio, attack, release) based on the detected modulation characteristics in each frequency band. When modulated speech is detected in a frequency band, low compression thresholds are applied; when steady noise is detected, higher thresholds are applied. This parameter adaptation resolves the contradiction by making compression settings contingent on local signal characteristics.
4Device complexity
If compression is applied uniformly across all frequency bands, then processing is simpler, but the hearing aid cannot differentiate between modulated and unmodulated sounds at different frequencies
Solution Approach 1:
The patent applies segmentation by dividing the audio signal into multiple frequency bands and processing each band separately with its own modulation detection and compression settings. This allows the system to differentiate between modulated and unmodulated sounds at different frequencies while maintaining manageable complexity through modular band-by-band processing. The segmentation approach resolves the contradiction by enabling frequency-selective processing without requiring overly complex global analysis.
Data Source
AI summary
A method of noise reduction of low-level input signals in a hearing aid involves applying compression to the input signal using a first compression ratio if a detected measure of amplitude modulation in the input signal is below a selected modulation level, and using a second compression ratio if the measure of amplitude modulation is above the selected modulation level. This reduces the volume of low-level steady-state noise while increasing the volume of modulated signals, e.g. speech. A hearing aid having a noise reduction system (10) has means for determining a level of amplitude modulation from a noise level and an absolute average level of an input signal, and comprises a dynamic compressor having a first compression ratio and a second compression ratio. The means for determining the level of amplitude modulation is configured to control the dynamic compressor in such a way that, below a predetermined input level, unmodulated sounds are amplified less than unmodulated sounds. In this way, low-level, unmodulated sounds are dampened by the hearing aid.