Wearable ANR Feedback Loop Modulation for Low-Frequency Overload
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Solution Overview
Problem
Conventional active noise reduction (ANR) devices fail to adequately manage noise under overload conditions, particularly due to adverse low frequency events, leading to audible artifacts such as oscillations and distortion.
Innovation Solution
Incorporating a feedback compensator with a tunable filter that modulates loop gain in response to adverse low frequency events, maintaining a similar loop gain shape near the low frequency cross-over to balance stability and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ANR devices use fixed loop gain for noise reduction, then noise reduction performance is maintained under normal conditions, but audible artifacts and oscillations occur under overload conditions caused by adverse low frequency events
Solution Approach 1:
The patent implements a tunable filter that dynamically adjusts the loop gain of the ANR system based on detected low frequency events. Instead of using a fixed loop gain, the system modulates the loop gain in real-time according to the adverse conditions detected, thereby maintaining stability and preventing audible artifacts while preserving noise reduction performance under normal conditions
Solution Approach 2:
The patent changes the loop gain parameter dynamically in response to detected low frequency events. By modulating the loop gain based on the adverse conditions, the system adapts its noise reduction characteristics to prevent overload conditions and associated audible artifacts while maintaining effective noise reduction during normal operation
2Reliability
If loop gain is increased to improve low frequency noise reduction, then noise reduction performance improves, but system stability deteriorates and oscillations occur
Solution Approach 1:
The tunable filter enables dynamic adjustment of the loop gain based on the detected low frequency events. By modulating the loop gain in real-time, the system can increase gain when needed for noise reduction while maintaining stability through adaptive control, preventing the oscillations that would occur with fixed high gain settings
Solution Approach 2:
The system uses feedback from the detected low frequency events to continuously adjust the loop gain. This feedback mechanism allows the system to maintain optimal stability margins while achieving effective low frequency noise reduction, as the loop gain is continuously adapted based on the actual system conditions rather than being fixed
3Reliability
If ANR system operates under overload conditions to handle adverse low frequency events, then noise reduction coverage is improved, but transient effects and distortion increase
Solution Approach 1:
The tunable filter detects adverse low frequency events and preemptively adjusts the loop gain before overload conditions occur. By modulating the loop gain in advance in response to detected events, the system prevents transient effects and distortion from occurring in the first place, rather than attempting to correct them after they occur
Solution Approach 2:
The system prepares for potential overload conditions by dynamically adjusting the loop gain in response to detected low frequency events. This beforehand adjustment acts as a cushioning mechanism that prevents the system from entering overload conditions that would cause transient effects and distortion, protecting the system in advance
Data Source
AI summary
Various aspects include a wearable audio device having active noise reduction (ANR). In some cases, a system includes: an electroacoustic transducer; and a tunable filter that processes an audio signal by: receiving a noise reduction signal configured to modify the audio signal and generate a noise reduced audio signal at the electroacoustic transducer; comparing the noise reduction signal to a threshold; and in response to the threshold being exceeded, generating an adjusted noise reduction signal using a modulated loop gain, the modulated loop gain determined based on an amount the frequency threshold was exceeded.