Sound Signal Processing Apparatus for Hearing Impairment Directionality
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Solution Overview
Problem
Individuals who are hard of hearing face difficulties in recognizing sound directionality due to low sensitivity to interaural time differences (ITD) and interaural level differences (ILD), making it challenging to determine the source of sound signals.
Innovation Solution
A method and apparatus that process sound signals received at both ears by determining phase or time differences, calculating level differences, and adjusting gains to output sound signals in a way that enhances the recognition of directionalities, even for low-frequency sounds, by using phase or time differences to determine and amplify interaural level differences (ILD).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sound signals are processed using traditional ITD or ILD methods, then normal hearing users can recognize sound directionality, but hard of hearing individuals cannot recognize sound directionality due to low sensitivity to ITD and high threshold of sound signals
Solution Approach 1:
The patent transforms the ITD parameter into an ILD parameter through mathematical conversion. The system calculates phase difference from ITD measurements and converts it to equivalent ILD values using the relationship: ILD = 20*log10(cos(π*ITD*f)), where f is frequency. This parameter transformation allows hard of hearing individuals to perceive directional information through ILD cues that they can detect, rather than relying on ITD cues they cannot perceive.
2Measurement precision
If sound signals are output with equal gains to both ears, then the system is simple to implement, but hard of hearing users cannot recognize directionalities of sound signals
Solution Approach 1:
The system performs preliminary calculation of phase difference and level difference before gain adjustment. It first measures ITD, then pre-calculates the corresponding phase difference and converts it to target ILD values. These pre-calculated values are used to determine the gain coefficients for each ear before signal output, ensuring that directional information is properly encoded in the ILD domain that hard of hearing users can perceive.
Solution Approach 2:
The patent replaces the natural mechanical/acoustic ITD detection mechanism with an electronic signal processing system that mathematically transforms ITD into ILD. Instead of relying on the user's biological ability to detect time differences, the system uses digital signal processing to convert time difference information into level difference information that can be perceived through amplitude variations.
3Measurement precision
If the system processes only high-frequency sounds, then ITD processing is effective, but low-frequency sounds cannot provide sufficient directional information for hard of hearing individuals
Solution Approach 1:
The patent creates a universal directional encoding system that works across all frequency ranges by converting ITD to ILD. The transformation formula ILD = 20*log10(cos(π*ITD*f)) is applicable to any frequency, allowing the system to provide directional information for both low-frequency and high-frequency sounds. This enables hard of hearing users to utilize directional cues from the full audible spectrum, not just high frequencies.
Data Source
AI summary
A method of processing a sound signal includes obtaining a phase difference or a time difference between sound signals received at both ears; determining a level difference between the sound signals based on the phase difference or time difference; determining gains of the sound signals to be output to both ears based on the level difference; and outputting the sound signals based on the determined gains.