Adaptive Filter Leakage Smoothing for Active Noise Reduction
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Solution Overview
Problem
Active noise reduction systems fail to completely eliminate noise, instead achieving significant attenuation but not complete noise reduction, and face challenges with nonlinear operation and audible artifacts such as clicks or pops.
Innovation Solution
An adaptive noise reduction system that uses a leakage adjuster with a low-pass filter to smooth leakage factor values, applying them to filter coefficients to modify and improve noise reduction, particularly by selecting appropriate leakage factors based on detectible conditions like system deactivation or nonlinear operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If adaptive filters are used for active noise reduction, then noise attenuation is achieved, but audible artifacts such as clicks or pops and nonlinearities occur
Solution Approach 1:
The patent applies leakage factor adjustment to modify the adaptation behavior of adaptive filters. By dynamically changing the leakage factor parameter based on system conditions (such as when the system is deactivated or when output signal magnitude exceeds thresholds), the filter transitions between different adaptation states, preventing nonlinear operation and audible artifacts while maintaining noise attenuation performance
Solution Approach 2:
The system continuously monitors the magnitude of the output audio signal and the state of the active noise reduction system, and uses this feedback to adjust the leakage factor. This closed-loop control ensures the adaptive filter operates within linear regions and avoids generating clicks or pops by detecting and responding to conditions that would cause nonlinear operation
2Object-affected harmful factors
If leakage factor values are adjusted dynamically, then noise reduction performance is improved, but system complexity increases
Solution Approach 1:
The patent implements dynamic adjustment of leakage factor values based on real-time system conditions. The leakage factor is changed from static to dynamic, allowing the system to adapt its behavior according to operating conditions such as system activation state and output signal magnitude, thereby improving noise reduction performance without requiring complex additional hardware
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 system significantly reduces audible artifacts and nonlinearities, achieving effective noise attenuation while controlling noise levels to prevent overdriving and maintaining a desired spectral profile, thereby enhancing noise reduction performance.
Implementation Method 1
smoothing the stream of leakage values, using a low pass filter, to provide a smoothed stream of leakage factor values
Data Source
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Figure 1B
Figure 2A
AI summary
An active noise reduction system using adaptive filters. A method of operation the active noise reduction system includes smoothing a stream of leakage factors. The frequency of a noise reduction signal may be related to the engine speed of an engine associated with the system within which the active noise reduction system is operated. The engine speed signal may be a high latency signal and may be obtained by the active noise reduction system over audio entertainment circuitry.