Binaural Hearing System Direction Estimation Using Pre-Measured Transfer Functions
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Solution Overview
Problem
Existing hearing aid systems face challenges in accurately estimating the direction of a target sound source, especially in noisy environments, due to the influence of the user's head and ambient noise, and require complex computational methods that are resource-intensive.
Innovation Solution
A binaural hearing system that uses a maximum likelihood approach with pre-measured relative transfer functions and information fusion techniques to estimate the direction-of-arrival of a target sound source, reducing computational load and wireless communication overhead while maintaining estimation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex computational methods are used to estimate direction of sound source, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent pre-calculates and stores relative transfer functions (RTFs) for multiple directions before actual operation. During direction estimation, the system only needs to compare received signals with pre-stored RTFs using simple correlation operations, rather than performing complex real-time computations. This preliminary preparation of reference data significantly reduces online computational complexity while maintaining estimation accuracy.
Solution Approach 2:
The system creates simplified copies of the complex acoustic environment by pre-measuring and storing RTFs that represent different propagation paths from various directions to the microphones. Instead of重新computing complex acoustic models during operation, the system uses these pre-computed RTF copies for rapid comparison and direction estimation, reducing real-time computational burden.
2Measurement precision
If binaural configuration with information exchange between hearing devices is used, then measurement precision is improved, but loss of information increases due to wireless transmission requirements
Solution Approach 1:
The patent extracts only the essential information needed for direction estimation—the correlation results between received signals and pre-stored RTFs—and transmits this extracted data between hearing devices via wireless communication. By taking out only the necessary statistical features rather than transmitting raw audio signals or complete computational data, the system minimizes wireless communication overhead and information loss while maintaining binaural estimation accuracy.
3Device complexity
If pre-measured relative transfer functions are used, then device complexity is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The system performs the complex and precision-sensitive RTF measurements in advance during a calibration phase, rather than requiring high precision during normal operation. This preliminary measurement of acoustic characteristics allows the device to use simpler, more robust correlation algorithms during actual direction estimation, reducing both computational complexity and real-time processing requirements while the initial measurement precision establishes the accuracy baseline.
Data Source
AI summary
A hearing system comprising a) a multitude M of microphones, M≥2, adapted for picking up sound from the environment and to provide corresponding electric input signals rm(n), m=1, . . . , M, n representing time, rm(n) comprising a mixture of a target sound signal propagated via an acoustic propagation channel and possible additive noise signals vm(n); b) a transceiver configured to receive a wirelessly transmitted version of the target sound signal and providing an essentially noise-free target signal s(n); c) a signal processor configured to estimate a direction-of-arrival of the target sound signal relative to the user based on c1) a signal model for a received sound signal rm at microphone m through the acoustic propagation channel, wherein the mth acoustic propagation channel subjects the essentially noise-free target signal s(n) to an attenuation αm and a delay Dm; c2) a maximum likelihood methodology; and c3) relative transfer functions dm representing direction-dependent filtering effects of the head and torso of the user in the form of direction-dependent acoustic transfer functions from each of M−1 of said M microphones (m=1, . . . , M, m≠j) to a reference microphone (m=j) among said M microphones, wherein it is assumed that the attenuation αm is frequency independent whereas the delay Dm may be frequency dependent. The application further relates to a method. Embodiments of the disclosure may e.g. be useful in applications such as binaural hearing systems, e.g. binaural hearing aids systems.