Adaptive Noise Reduction Using Engine Speed and Smoothed Leakage
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Solution Overview
Problem
Active noise reduction systems face challenges in effectively attenuating noise in vehicle cabins due to non-linear operation and the need for adaptive filtering techniques that can respond to varying noise levels and triggering conditions.
Innovation Solution
The system employs an adaptive filter with a leakage adjuster that calculates and applies smoothed leakage factors to filter coefficients, allowing for dynamic noise reduction based on thresholds and predefined events, such as changes in entertainment signal magnitudes or noise levels, to optimize noise cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If adaptive filters with dynamically adjusted leakage factors are used, then noise attenuation performance is improved, but system complexity increases
Solution Approach 1:
The patent implements dynamic adjustment of leakage factors based on real-time system state monitoring. The leakage factor is modified according to the correlation between reference and error signals, allowing the adaptive filter to optimize its performance adaptively rather than using fixed parameters. This dynamic approach resolves the contradiction by enabling improved noise attenuation through complexity that is only introduced when beneficial.
Solution Approach 2:
The system incorporates feedback mechanisms where the error signal from the adaptive filter is continuously monitored and used to adjust the leakage factor. This closed-loop control allows the system to automatically optimize its performance based on actual noise conditions, achieving better attenuation without requiring complex manual tuning or overly complicated system architecture.
2Reliability
If multiple threshold comparisons and smoothing techniques are applied, then system linearity is maintained, but processing time increases
Solution Approach 1:
The patent applies smoothing techniques to the leakage factor adjustments before they are fully implemented in the filter coefficients. This preliminary processing of the adjustment signals prevents abrupt changes that could cause non-linear operation or audible artifacts, while the smoothing itself is designed to be computationally efficient. The system prepares the adjustments in advance through controlled smoothing rather than immediate application.
Solution Approach 2:
The system monitors multiple parameters including the correlation between reference and error signals, and dynamically changes the leakage factor parameter based on these conditions. By carefully selecting which parameters to monitor and how to change the leakage factor, the system maintains linearity through multiple threshold comparisons while minimizing the computational burden through selective parameter adjustment rather than continuous full-system reprocessing.
3Object-affected harmful factors
If leakage factors are frequently adjusted, then noise reduction effectiveness is improved, but audible artifacts increase
Solution Approach 1:
The patent implements periodic or controlled adjustment of leakage factors rather than continuous frequent changes. The system monitors noise conditions and adjusts leakage factors at appropriate intervals or when specific threshold conditions are met, preventing the kind of rapid fluctuations that generate audible artifacts like clicks or distortion. This periodic approach maintains effectiveness by adjusting when needed while avoiding excessive adjustment frequency.
Solution Approach 2:
The system applies smoothing operations as a form of cushioning before the leakage factor adjustments are fully applied to the filter. This smoothing acts as a buffer that prevents abrupt changes from causing audible artifacts, while still allowing the leakage factor to be adjusted frequently enough to maintain effective noise reduction. The cushioning effect of smoothing protects against the harmful side effects of frequent adjustments.
Data Source
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.