Spatial Synthesis Filter for Hearing Aid Microphone Signals
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Solution Overview
Problem
Hearing aids with external microphone arrangements struggle to provide natural sound perception in noisy environments due to the lack of spatial auditory cues, leading to an artificial internalization of sound sources.
Innovation Solution
A method that generates and superimposes spatial auditory cues onto externally picked-up sound signals by determining the response characteristics of a spatial synthesis filter through cross-correlation between external and hearing aid microphone signals, allowing for the production of synthesized microphone signals with appropriate spatial cues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an external microphone arrangement is used to pick up sound signals from a distance, then the signal-to-noise ratio is improved, but spatial auditory cues are lost resulting in artificial sound perception
Solution Approach 1:
The patent uses the hearing aid's own microphone as an intermediary to capture spatial auditory cues that are then combined with the external microphone signal. The local microphone picks up the sound signal at the hearing aid's position, preserving spatial information, while the external microphone provides high SNR. These two signals are combined through spatial synthesis filtering to produce a final output that has both high quality and natural spatial perception.
2Loss of information
If spatial synthesis filtering is applied to restore spatial cues, then natural sound perception is improved, but computational complexity increases
Solution Approach 1:
The patent implements self-service by using the hearing aid device itself to generate the spatial synthesis filter. The filter is created by processing the signal from the hearing aid's own microphone, which automatically adapts to the user's specific listening environment and spatial characteristics. This eliminates the need for external calibration equipment or complex pre-programming, as the device serves itself to create the necessary spatial cues.
Solution Approach 2:
The spatial synthesis filter is computed in advance using cross-correlation between the external microphone signal and the local microphone signal. This preliminary computation of filter coefficients allows the system to quickly apply spatial synthesis during normal operation without real-time computational burden. The filter characteristics are determined beforehand based on the captured spatial information.
3Measurement precision
If cross-correlation processing is used to determine filter characteristics, then spatial cue accuracy is improved, but processing time increases
Solution Approach 1:
The patent applies partial action by using only the essential cross-correlation operation to determine the dominant spatial characteristics, rather than performing exhaustive spatial analysis. The cross-correlation quickly identifies the main time-delay and amplitude relationships between microphones, which are the most critical spatial cues. This selective approach achieves sufficient spatial accuracy without unnecessary computational overhead.
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 enhances the signal-to-noise ratio and provides a more natural sound perception by adding spatial cues to the reproduced sound, improving the ability to discriminate between sound sources and enhancing speech understanding in noisy environments without requiring binaural communication between hearing instruments.
Implementation Method 1
A hearing instrument or aids typically comprise a microphone arrangement which includes one or more microphones for receipt of incoming sound such as speech and music signals. The incoming sound is converted to an electric microphone signal
Implementation Method 2
transmitting the external microphone signal to a wireless receiver of a first hearing instrument via a first wireless communication link
Implementation Method 3
determining response characteristics of a first spatial synthesis filter by correlating the external microphone signal and a first hearing aid microphone signal of the first hearing instrument
Implementation Method 4
filtering the external microphone signal by the first spatial synthesis filter to produce a first synthesized microphone signal comprising first spatial auditory cues
Data Source
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AI summary
The present invention relates to a method of superimposing spatial auditory cues to an externally picked-up sound signal (sE(t)) in a hearing instrument (107, 109). The method comprises steps of a generating an external microphone signal (sE(t)) by an external microphone arrangement (105) and transmitting the external microphone signal (sE(t)) to a wireless receiver of a first hearing instrument (107) via a first wireless communication link (104). Further steps of the methodology comprise determining response characteristics of a first spatial synthesis filter (gL(t)) by correlating the external microphone signal (sE(t)) and a first hearing aid microphone signal (sL(t)) of the first hearing instrument (107) and filtering the external microphone signal (sE(t)) by the first spatial synthesis filter (gL(t)) to produce a first synthesized microphone signal (yL(t)) comprising first spatial auditory cues.