Adaptive Notch Filter for Convergent Howling Suppression
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Solution Overview
Problem
Existing howling suppression devices using adaptive notch filters face challenges in achieving effective howling suppression when the notch bandwidth is not constant, as the convergence of the adaptive notch filter is not guaranteed due to separate updates of frequency and bandwidth.
Innovation Solution
An adaptive notch filter that can dynamically modify notch frequencies and bandwidths without pre-setting the notch bandwidth, utilizing a transfer function that updates filter coefficients based on a step gain and filter coefficient update algorithms to adaptively suppress howling frequencies across a wide bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the notch bandwidth of the adaptive notch filter is set to a fixed value, then the filter structure is simple, but sufficient howling suppression performance cannot be obtained when howling characteristics vary
Solution Approach 1:
The patent makes the notch bandwidth dynamic by introducing a time-varying parameter α(n) that adapts to different howling characteristics. The bandwidth is updated according to the formula bandwidth(n) = α(n) × bandwidth(n-1), allowing the filter to adjust its bandwidth automatically based on the current howling conditions rather than being fixed, thus resolving the contradiction between simple structure and effective suppression performance.
Solution Approach 2:
The patent changes the bandwidth parameter from a fixed value to a time-varying parameter that can be adjusted dynamically. By updating the bandwidth parameter according to howling characteristics and using the relationship between pole position and bandwidth, the filter can adapt to varying howling conditions while maintaining a relatively simple overall structure.
2Adaptability or versatility
If separate update formulas are used for frequency and bandwidth, then the notch bandwidth can be adapted, but convergence of the adaptive notch filter is not guaranteed
Solution Approach 1:
The patent merges the frequency and bandwidth updates into a unified adaptive process. By updating the pole position directly using an adaptive algorithm and then deriving both frequency and bandwidth from this single updated pole position, the system ensures that frequency and bandwidth changes are coordinated and consistent, guaranteeing filter convergence while maintaining adaptability.
Solution Approach 2:
The patent employs feedback mechanisms where the updated pole position information is used to simultaneously determine both frequency and bandwidth. The adaptive algorithm continuously monitors the system performance and adjusts the pole position accordingly, creating a closed-loop control that ensures convergence while adapting to changing howling characteristics.
3Stability of the object's composition
If the adaptive notch filter uses a fixed notch bandwidth, then the filter coefficient update is stable, but it cannot suppress howling frequencies with varying bandwidths
Solution Approach 1:
The patent introduces dynamics into the bandwidth parameter while maintaining stability in the update process. By updating the pole position using a stable adaptive algorithm and then calculating bandwidth from the pole position relationship, the system achieves both stability in the update mechanism and adaptability in the bandwidth value, allowing suppression of howling with varying bandwidths.
Solution Approach 2:
The patent changes the bandwidth from a fixed parameter to a dynamically calculated parameter based on pole position. This allows the bandwidth to vary according to howling characteristics while the underlying update algorithm remains stable, resolving the contradiction between update stability and adaptability to varying bandwidths.
Data Source
AI summary
An adaptive notch filter adaptively modifies one or more notch frequencies. The adaptive notch filter includes a transfer function equivalent to coupling j stages (where j is a natural number equal to or greater than 1) of adaptive notch filter units each having a transfer function Hf(z) expressed by a predetermined equation and having a different notch frequency.