Individual HRTF Determination for Hearing Aid Spatial Audio
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Solution Overview
Problem
Hearing aid users experience poor sound localization and internalization of sound sources, leading to listening fatigue and discomfort, due to the inability to accurately reproduce individual Head-Related Transfer Functions (HRTFs), which are crucial for spatial sound perception.
Innovation Solution
A method to determine individual HRTFs by obtaining approximate HRTFs, measuring deviations, and modifying them to create accurate individual HRTFs, allowing for improved sound localization and externalization without the need for expensive and cumbersome anechoic chamber measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional hearing aids reproduce sound, then speech intelligibility is achieved, but sound sources are internalized and localization ability deteriorates
Solution Approach 1:
The patent applies parameter changes by modifying the acoustic transfer functions used in hearing aid signal processing. Specifically, it transforms the conventional monaural or simplified binaural processing into individualized binaural processing using measured HRTFs (Head-Related Transfer Functions). This changes the acoustic parameters to include spectral cues, interaural time differences, and interaural level differences that enable externalization and accurate localization while maintaining speech intelligibility.
Solution Approach 2:
The patent implements preliminary action by measuring and storing individual HRTF data for each user before actual hearing aid operation. The system performs preliminary binaural rendering calculations and creates personalized acoustic profiles in advance, so that when the hearing aid operates, it can immediately apply the correct spatial transformation without real-time computation delays, thereby achieving both intelligibility and proper localization.
2Ease of operation
If binaural sound signals are reproduced with approximate HRTFs, then externalization is improved, but measurement precision and reliability are reduced
Solution Approach 1:
The patent applies self-service by having the system automatically measure the user's individual HRTF characteristics through integrated microphones and processors. Instead of relying on generic or approximate HRTF data from databases, the system performs self-measurement during fitting or calibration sessions, capturing the user's unique anatomical and acoustic properties. This self-measured data then serves as the basis for accurate binaural rendering, ensuring both externalization and precision without requiring manual intervention or expensive external facilities.
3Measurement precision
If anechoic chamber measurements are performed to obtain accurate HRTFs, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses an intermediary approach by employing a portable measurement system that acts as a mediator between the user and the HRTF determination process. Instead of requiring expensive anechoic chambers, the system uses a portable acoustic measurement setup with microphones positioned in or near the ear canals, connected to a processor that performs the HRTF extraction. This intermediary measurement system bridges the gap between simple consumer devices and complex laboratory equipment, providing accurate measurements in ordinary environments.
Solution Approach 2:
The patent replaces the mechanical/acoustic complexity of anechoic chambers with electronic signal processing. Instead of requiring physically complex anechoic environments with specialized acoustic treatments, the system uses electronic microphones, digital signal processors, and computational algorithms to measure and determine HRTFs in ordinary rooms. This substitution of mechanical acoustic control with electronic measurement and processing dramatically reduces device complexity and cost while maintaining measurement precision.
Data Source
AI summary
A method of determining a set of individual HRTFs for a specific human includes: obtaining a set of approximate HRTFs; obtaining at least one measured HRTF of the specific human; determining a deviation of one of the at least one measured HRTF with relation to a corresponding one of the set of approximate HRTFs; and forming the set of individual HRTFs by modification of the set of approximate HRTFs based at least in part on the determined deviation.