Dual FIR Filter Windowing for Inaudible Coefficient Switching
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Solution Overview
Problem
Dynamic frequency-dependent gain in contact hearing systems using FIR filters can introduce audible artifacts due to changing filter coefficients, which are not effectively mitigated by existing methods.
Innovation Solution
The implementation of a dual FIR filter system with complementary windows, where coefficient changes are applied only during the attenuation phase of each filter, ensuring that artifacts are minimized by making the filter changes inaudible.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If filter coefficients are changed dynamically to achieve frequency-dependent gain, then adaptability is improved, but audible artifacts are introduced
Solution Approach 1:
The single filter is divided into two parallel FIR filters with different coefficient sets. Each filter processes the input signal simultaneously, but their outputs are combined with complementary windows that are active at different times. This segmentation allows the system to switch between different coefficient sets without introducing audible artifacts, as the transition is spread across two filters with smooth window-based mixing.
Solution Approach 2:
The system implements periodic switching between two filter coefficient sets using complementary window functions. The windows alternate in a periodic manner, with one window being active while the other is inactive, and vice versa. This periodic action allows the filter coefficients to change dynamically while maintaining smooth transitions that prevent audible artifacts.
2Object-generated harmful factors
If filter coefficient changes are slowed and smoothed to reduce artifacts, then artifact reduction is improved, but response speed deteriorates
Solution Approach 1:
The system dynamically switches between two filter coefficient sets using time-varying window functions. Rather than slowly smoothing the transition between coefficient sets, the system uses dynamic windowing to control the contribution of each filter output. This allows for rapid coefficient changes while maintaining smooth transitions through the window functions, thus improving response speed without sacrificing artifact reduction.
3Object-generated harmful factors
If a dual filter system with windowing is implemented, then artifact reduction is improved, but device complexity increases
Solution Approach 1:
The system merges two FIR filters into a single processing path by combining their outputs with complementary window functions. Rather than having two independent filter systems, the filters share the same input and output paths, with their contributions controlled by the windowing function. This merging approach reduces the overall complexity compared to having completely separate filter systems while still achieving artifact reduction through the dual-filter architecture.
Data Source
AI summary
The current invention is intended to render artifacts, which are introduced by changes in coefficients in an FIR filter, inaudible by applying a window to the filtered signal that results in the output of the filter (e.g. FIR filter), in which the coefficients are being changed, supplying little or none of the total output while the output of the filter, in which the coefficients are stable, supplies most or all of the total output.