Binaural Hearing Aid Phase Shift Signal Separation
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Solution Overview
Problem
Hearing impaired individuals face significant challenges in understanding speech in noisy environments, as existing digital hearing aids using multi-channel amplification and compression, beamforming, or spectral subtraction techniques often fail to effectively separate target signals from noise, neglecting the listener's intent and potentially removing important audio cues.
Innovation Solution
A binaural hearing aid system that utilizes interaural time and level differences to phase shift target and noise signals, presenting them in a way that enhances the user's ability to distinguish speech from noise through phase manipulation, allowing the auditory system to naturally separate signals, thereby improving speech intelligibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If beamforming or spectral subtraction techniques are applied to enhance target signal and suppress noise, then speech reception threshold is improved, but parts of the audio signal that the listener is trying to focus on may be removed
Solution Approach 1:
The patent replaces traditional mechanical signal processing approaches (beamforming, spectral subtraction) with a psychoacoustic approach that exploits the human auditory system's binaural processing capabilities. Instead of manually filtering signals, the system presents phase-shifted signals to each ear, allowing the auditory system to naturally separate target from noise through binaural masking level difference effects.
Solution Approach 2:
The patent changes the phase parameter of the audio signal presented to each ear. By presenting the target signal in-phase to one ear and out-of-phase to the other ear (or vice versa for noise), the system creates interaural phase differences that the auditory system uses to separate signals. This parameter change enables signal enhancement without removing audio information.
2Object-affected harmful factors
If traditional noise reduction techniques are applied, then noise disturbance is reduced, but listener intent is not taken into account
Solution Approach 1:
The patent enables the auditory system to perform noise reduction itself by presenting binaural signals with specific phase relationships. The auditory system's natural binaural processing mechanisms automatically separate target signal from noise based on interaural phase differences, eliminating the need for complex algorithms to interpret listener intent while still achieving adaptive noise reduction.
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 can increase the Binaural Masking Level Difference by up to 20 dB, significantly improving the user's ability to understand speech in noise by presenting the target signal phase-shifted and the noise in-phase, or vice versa, facilitating natural noise reduction and signal separation.
Implementation Method 1
The most important cues in binaural processing are the interaural time differences (ITD) and the interaural level differences (ILD). The ITD results from the difference in distance from the source to the two ears.
Implementation Method 2
The level difference is a result of diffraction and is determined by the relative position of the ears compared to the source. This cue is dominant above 2 kHz but the auditory system is equally sensitive to changes in ILD over the entire spectrum.
Implementation Method 3
The level difference is a result of diffraction and is determined by the relative position of the ears compared to the source.
Implementation Method 4
a phase shift circuit configured to phase shift the estimate of one of the target signal and the noise signal
Implementation Method 5
It has been shown that manipulating the relative interaural phase and level of a target signal, i.e. a signal a listener desires to listen to, and of a noise signal, i.e. a signal the listener perceives as disturbing, can improve speech intelligibility significantly.
Data Source
AI summary
A method of binaural signal enhancement in a binaural hearing aid system, includes providing at least one microphone audio signal in response to sound, providing an estimate of one of a target signal and a noise signal based on the at least one microphone audio signal, phase shifting the estimate of one of the target signal and the noise signal, providing a phase shifted signal in which the phase shifted estimate of one of the target signal and the noise signal substantially substitutes the respective one of the target signal and the noise signal, transmitting a first signal representing the phase shifted signal towards a first eardrum of a user of the binaural hearing aid system, and transmitting a second signal representing the at least one microphone audio signal towards a second eardrum of the user. A system for performing the method is also described.