Active Vibration Noise Control Device with Adaptive Step-Size
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Solution Overview
Problem
Existing active vibration noise control devices experience a decrease in noise-canceling effectiveness due to unstable operation of adaptive notch filters in narrow vehicle interiors, particularly when deep dips in transfer characteristics occur, leading to increased error signals and phase discontinuities during speaker switching.
Innovation Solution
An active vibration noise control device employing multiple speakers with adaptive notch filters, a microphone for error signal detection, and a step-size parameter adjustment mechanism to stabilize filter coefficient updates during frequency bands with dips, ensuring continuous noise cancellation without phase discontinuity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If speaker switching is performed based on noise frequency to avoid dip characteristics, then the stability of adaptive notch filter operation is improved, but the error signal increases due to filter coefficient readaptation discontinuity
Solution Approach 1:
The patent applies preliminary action by pre-storing filter coefficients that correspond to different speakers and frequency conditions. When a speaker switch is needed, the system retrieves the pre-prepared filter coefficients matching the new speaker's characteristics, avoiding the need for real-time readaptation and preventing error signal increases.
Solution Approach 2:
The patent implements dynamics by making the filter coefficients adaptive and switchable based on which speaker is currently in use. The system dynamically selects appropriate filter coefficients from stored sets corresponding to different speakers, allowing the filter to adapt to changing speaker characteristics without causing instability or error increases.
2Reliability
If deep dip characteristics occur in transfer characteristics from speaker to microphone, then the noise-canceling effect decreases, but switching speakers to avoid dip frequency bands causes filter coefficient discontinuity
Solution Approach 1:
The system performs preliminary action by pre-calculating and storing optimal filter coefficients for each speaker across different frequency conditions. When switching speakers, the system immediately applies the pre-prepared coefficients corresponding to the new speaker, avoiding filter coefficient discontinuity and maintaining stable noise cancellation without needing to switch frequency bands.
Solution Approach 2:
The patent applies parameter changes by modifying the filter coefficients based on which speaker is currently active. The system changes the filter parameters to match the acoustic characteristics of the current speaker, allowing continuous effective noise cancellation across speaker transitions without being constrained by dip frequency bands of any single speaker.
Data Source
AI summary
The disclosed active vibration noise control device is suitable for use in cancelling out vibration noise by outputting control noise from a plurality of speakers. When a vibration noise frequency is in a dip bandwidth, the active vibration noise control device alters the step size parameters used to update the filter coefficient at at least one filter coefficient update means from among a plurality of filter coefficient update means. Thus, the filter coefficient update speed can be retarded in unstable dip bandwidths, enabling loss in silencing effect which occurs during dip characteristics to be appropriately reduced.