Binaural Hearing Aid Localization via Frequency-Segmented Wiener Filtering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional hearing aids struggle to enhance signal-to-noise ratio for lateral sound sources, leading to loss of binaural cues and ambiguity in spatial sound localization due to limitations in directional microphones and noise suppression methods.
Innovation Solution
A binaural system that processes high and low frequency components differently, using Wiener filtering with pre-processing based on differential directional microphones and head shadowing effects to preserve interaural level differences and enhance noise suppression, applying the same amplification factor to both ears to maintain sound localization capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If differential processing by subtracting microphone signals is used to achieve directional sensitivity, then directional sensitivity is improved, but spatial ambiguities arise when wavelength becomes too short compared to microphone spacing
Solution Approach 1:
The frequency spectrum is segmented into different bands, with different processing strategies applied to each band. Low frequency signals are processed using differential processing, while high frequency signals use other methods, avoiding spatial aliasing in the high frequency range while maintaining directional sensitivity at low frequencies.
Solution Approach 2:
Different processing qualities are applied to different frequency components. Low frequency components receive differential processing for directional sensitivity, while high frequency components receive processing that avoids spatial ambiguities, optimizing performance for each frequency range independently.
2Measurement precision
If signals are transmitted from one ear to both ears to emphasize lateral signals, then lateral signal emphasis is improved, but binaural cues for sound localization are lost
Solution Approach 1:
The system changes parameters selectively for different frequency components. Low frequency lateral signals are emphasized through transmission to both ears, while high frequency components maintain their original spatial characteristics to preserve binaural localization cues, achieving both lateral emphasis and localization preservation.
3Productivity
If the same gain factor is applied to both ears for noise suppression, then noise suppression consistency is improved, but interaural level differences may be compromised
Solution Approach 1:
Different gain factors are applied to different frequency components and different ears based on local conditions. Low frequency noise suppression uses consistent gain factors, while high frequency processing preserves interaural level differences through ear-specific gain adjustments, optimizing both noise suppression and localization.
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
The solution effectively increases noise suppression for lateral signals while retaining sound localization abilities by applying directional filtering across the entire frequency range, improving the signal-to-noise ratio and maintaining interaural level differences.
Implementation Method 1
By utilizing the head shadowing effect at high frequencies, the signals from the two microphones can be used to determine the useful and interfering signal levels
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A method and system for improving signal-to-noise ratio of output signals of a microphone system having two or more microphones due to acoustic useful signals at sides of the system are used in hearing instruments, especially hearing aids worn on the head. High and low frequency portions (cut-off frequency between 700 Hz and 1.5 kHz, approx. 1 kHz) are processed differently. In low frequency ranges, differential microphone signals directed towards left right are produced to determine lateral useful and noise sound levels using these two directional signals. These levels are used for subjecting every microphone signal to individual Wiener filtering. The natural head shadowing effect is used in high frequency ranges as a pre-filter for noise and useful sound estimation for subsequent Wiener filtering. The methods are used in hearing instruments worn on the head individually for high or low frequencies or in combination and complement each other.