Handset Acoustic Equalization for Hearing Aid Compatibility
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Solution Overview
Problem
Handsets fail to meet regulatory requirements for both acoustic and magnetic frequency response characteristics when used with hearing aids, particularly exhibiting a drop in acoustic frequency response between 1000 and 3000 Hz and non-flat magnetic frequency response, which complicates compliance with standards like those in Australia.
Innovation Solution
A technique involving a digital signal processor to equalize the received signal, ensuring both acoustic and magnetic frequency responses are flat over the audible range, utilizing a filter to correct the acoustic frequency response and maintain compliance, with components including a voice coil, hearing aid coil, and an LC filter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a low acoustic impedance receiver is used in the handset, then the handset can provide good audio quality and allow users to hear low frequencies, but the acoustic frequency response exhibits a drop between 1000 and 3000 Hz, failing to meet regulatory requirements
Solution Approach 1:
The patent applies parameter changes by using a digital signal processor to equalize the received signal, adjusting the frequency response parameters to compensate for the drop between 1000 and 3000 Hz. The DSP modifies the signal characteristics to achieve a substantially flat frequency response across the audible range, thereby meeting regulatory requirements while maintaining the benefits of low acoustic impedance receiver design
2Adaptability or versatility
If the handset uses inductive coupling with a hearing aid coil, then the handset can couple with hearing aids, but the magnetic frequency response becomes non-flat, complicating compliance with regulatory standards
Solution Approach 1:
The patent employs feedback mechanisms through the digital signal processor that monitors and adjusts the magnetic frequency response. The DSP processes the signal to maintain a substantially flat magnetic frequency response across the audible range while preserving hearing aid coupling capabilities, thus meeting regulatory standards
3Ease of manufacture
If the handset contains the solution within the handset itself, then the integration is simplified and wiring issues are avoided, but the device complexity increases due to inclusion of DSP and filter components
Solution Approach 1:
The patent merges the equalization and filtering functions into integrated components within the handset. The digital signal processor and LC filter are combined into a unified system that performs both acoustic and magnetic frequency response correction, simplifying integration and avoiding complex external wiring while managing device complexity through functional integration
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
The solution ensures the handset meets regulatory standards for both acoustic and magnetic frequency responses, allowing compatibility with hearing aids while simplifying integration by containing the solution within the handset, avoiding complex wiring issues.
Implementation Method 1
The receiver includes a voice coil and a hearing aid coil
Implementation Method 2
inductive coupling where a hearing aid coil in a handset generates a magnetic field that couples the received voice signal to the hearing aid
Implementation Method 3
filtering the compensated received signal applied to the hearing aid coil
Data Source
AI summary
In one embodiment, an equalizer outputs a compensated received signal that flattens the acoustic frequency response characteristic of a handset having a leak tolerant ear piece. A hardware based filter is implemented within the handset having a response matched to the response of the equalizer so that the acoustic and magnetic frequency responses of the handset are substantially flat over the audible frequency range to comply with regulatory requirements.