Active Noise Reduction Device Dynamic Step Size Adjustment
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Solution Overview
Problem
Conventional active noise reduction devices face challenges when applied in environments with audio signals, as they can attenuate the audio signal and prolong the generation time of residual abnormal noise due to reduced step size parameters.
Innovation Solution
An active noise reduction device and method that includes a standard signal generator, adaptive filter unit, control sound output unit, and error signal detector, which generates a control signal based on both engine vibration and audio information features, adjusting the step size parameter to minimize error signals and reduce residual noise effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the step size parameter μ is decreased to reduce attenuation of audio signals, then the audio signal quality is improved, but the convergence rate of the adaptive filter becomes slow and the generation time of residual abnormal noise is prolonged
Solution Approach 1:
The patent applies dynamics by making the step size parameter μ variable rather than fixed. The controller dynamically adjusts μ based on the detected audio signal characteristics: when audio signals are detected, μ is set to a smaller value to prevent attenuation, and when no audio signals are present, μ is set to a larger value to accelerate convergence and reduce residual noise generation time. This dynamic adjustment resolves the contradiction between audio signal quality and noise reduction speed.
Solution Approach 2:
The patent changes the parameter μ (step size parameter) based on the operating conditions. By detecting the presence and characteristics of audio signals, the system adjusts the step size parameter to optimize performance: smaller μ for audio protection and larger μ for faster noise reduction. This parameter change strategy directly addresses the technical contradiction by adapting the system behavior to different operational states.
2Object-affected harmful factors
If the step size parameter μ is decreased to protect audio signals, then the audio signal attenuation is reduced, but the follow-up rate of the adaptive filter decreases
Solution Approach 1:
The system dynamically adjusts the step size parameter μ based on real-time detection of audio signals. When audio signals are present, μ is reduced to protect them from attenuation. When audio signals are absent or below a threshold, μ is increased to improve the follow-up rate and convergence speed. This dynamic parameter adjustment resolves the contradiction between audio signal protection and filter responsiveness.
Solution Approach 2:
The patent implements parameter changes by modifying the step size parameter μ according to the detected audio environment. The controller monitors audio signal levels and adjusts μ accordingly: smaller values during audio playback to prevent attenuation, and larger values during silence or low-volume conditions to enhance the adaptive filter's follow-up rate and overall performance.
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 solution effectively reduces residual abnormal noise in environments with audio signals by dynamically adjusting the step size parameter based on audio information, enhancing the follow-up rate of the adaptive filter and shortening the generation time of residual noise.
Implementation Method 1
The active noise reduction device actively reduces a noise at a control point by causing a control sound to interfere with a control target sound
Data Source
AI summary
An active noise reduction device includes a standard signal generator, an adaptive filter unit, a control sound output unit, and an error signal detector. The adaptive filter unit includes a control signal generator, a filter coefficient update unit, and a step size setting unit. The control signal generator multiplies a standard signal by a filter coefficient to generate a control signal. Based on a reference signal and an error signal, the filter coefficient update unit updates the filter coefficient so as to minimize the error signal. The step size determiner sets a step size parameter indicating an update amount of the filter coefficient. The filter coefficient update unit sets a step size adjustment coefficient for adjusting the step size parameter based on an audio information feature amount and a change of the control signal.