Frequency-Domain Adaptive Noise Cancellation With Event-Driven Filter Control
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Solution Overview
Problem
Conventional adaptive noise cancellation (ANC) systems are complex, power-intensive, and can produce undesirable results due to rapid environmental changes, such as ambient tone, howling, and wind noise, which affect the adaptive filter's performance and generate interference.
Innovation Solution
The ANC system adjusts its adaptive filter based on a signal-to-disturbance ratio (SDR) to optimize performance, using a controller to detect acoustic events and apply spectrum gain constraints, and operates in the frequency domain to improve robustness and convergence, rather than the time domain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional time-domain ANC systems are used, then noise cancellation can be provided, but the systems become complex and consume significant power
Solution Approach 1:
The patent replaces the conventional time-domain processing approach with frequency-domain processing. This substitution transforms the mathematical operations from time-domain adaptive filtering to frequency-domain processing using FFT (Fast Fourier Transform), which reduces computational complexity and power consumption while maintaining noise cancellation effectiveness
Solution Approach 2:
The patent changes the domain parameter from time-domain to frequency-domain processing. By transforming the signal processing approach to operate in the frequency domain, the system achieves the same noise cancellation function with reduced computational requirements and lower power consumption
2Adaptability or versatility
If the adaptive filter continuously adapts to environmental changes, then the system can respond to noise variations, but it generates undesirable results under certain circumstances such as acoustic disturbances
Solution Approach 1:
The patent implements a feedback mechanism where the system continuously monitors the acoustic environment and detects specific disturbance patterns (acoustic events). When disturbances are detected, the system provides feedback to adjust the adaptive filter behavior, freezing or reducing adaptation in affected frequency bins to prevent generating undesirable noise while maintaining adaptability to normal environmental changes
Solution Approach 2:
The patent makes the adaptive filter dynamics adjustable by introducing event-driven control. The filter adaptation rate is dynamically changed based on detected acoustic events - normally adapting to track environmental changes, but freezing or reducing adaptation when disturbances are detected, thus preventing harmful output while maintaining necessary adaptability
3Speed
If the adaptive filter adapts rapidly to track environmental changes, then the system can maintain performance, but it may diverge or generate interference during rapid acoustic events
Solution Approach 1:
The patent implements dynamic control of the adaptation rate by detecting acoustic events in real-time. When rapid acoustic events are detected, the system dynamically reduces or freezes the adaptation rate in affected frequency bins, preventing divergence while maintaining fast convergence during normal conditions. This dynamic adjustment resolves the contradiction between rapid adaptation and system stability
Data Source
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AI summary
The handling of disturbances to audio signals may be improved with an adaptive noise cancellation (ANC) system that performs frequency-domain adaption. The ANC systems may be configured to determine if a disturbance is present at a first frequency in the second input signal received from the reference microphone. The ANC systems may update an algorithm of an adaptive filter based, at least in part, on the first input signal, the second input signal, and a feedback signal that is based on an output of the adaptive filter by changing parameters of the algorithm such that the adaptive filter adapts around the first frequency differently than other frequencies when the disturbance is present.