Spatial Synthesis Filter for Hearing Aid External Microphones
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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 correlation with the hearing aid microphone signal, 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 creates a virtual copy of the acoustic environment by synthesizing spatial cues through filtering. The external microphone signal is processed with a spatial synthesis filter that replicates the acoustic characteristics (impulse response) of the target sound source location, producing a synthesized signal that contains artificial spatial cues matching the original acoustic scene.
Solution Approach 2:
The spatial synthesis filter acts as an intermediary between the external microphone signal and the user's perception. It mediates by convolving the external microphone signal with the impulse response of the target sound source location, thereby inserting the missing spatial information that would otherwise be lost due to the external microphone's remote position.
2Reliability
If the external microphone is placed far from the user's ear, then it can capture sound sources with better signal-to-noise ratio, but the sound appears internalized and unnatural to the user
Solution Approach 1:
The patent synthesizes a virtual acoustic environment by copying the impulse response characteristics of the target sound source location and applying them to the external microphone signal. This creates an artificial acoustic scene that mimics what the user would hear if the sound source were actually present at the captured location, restoring natural spatial perception.
3Loss of information
If spatial synthesis filtering is applied to external microphone signals, then spatial auditory cues are restored, but processing complexity increases
Solution Approach 1:
The patent performs preliminary measurement of the impulse response at the target sound source location and stores it for later use. This pre-characterization of the acoustic environment allows the spatial synthesis filter to be configured once, simplifying real-time processing during actual use while still providing accurate spatial cue restoration.
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 externally recorded sound signals, improving the hearing aid user's ability to distinguish between sound sources in noisy environments.
Implementation Method 1
generating an external microphone signal by an external microphone arrangement placed in a sound field
Implementation Method 2
determining response characteristics of a first spatial synthesis filter by correlating the external microphone signal and a first hearing aid microphone signal
Implementation Method 3
filtering the received external microphone signal by the first spatial synthesis filter to produce a first synthesized microphone signal comprising first spatial auditory cues
Data Source
AI summary
The present disclosure relates in a first aspect to a method of superimposing spatial auditory cues to an externally picked-up sound signal in a hearing instrument. The method comprises steps of a generating an external microphone signal by an external microphone arrangement and transmitting the external microphone signal to a wireless receiver of a first hearing instrument via a first wireless communication link. Further steps of the methodology comprise 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 and filtering the external microphone signal by the first spatial synthesis filter to produce a first synthesized microphone signal comprising first spatial auditory cues.