Vehicle Active Noise Control with Compressed Reference Signals
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Solution Overview
Problem
Conventional active noise reduction devices face challenges in effectively managing large amplitude reference signals, which can lead to abnormal sounds due to excessive canceling sound output, and require efficient updating of adaptive filter coefficients to maintain noise reduction efficacy.
Innovation Solution
The proposed active noise reduction device incorporates a compressor to manage reference signals with amplitudes greater than or equal to a threshold, an adaptive filter unit to generate canceling signals, and a filter coefficient updater that adjusts the step size parameter using the reference signal, along with a μ adjuster to optimize the update process, ensuring appropriate noise reduction without abnormal sound perception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a compressor is used to compress reference signals with amplitude greater than or equal to a threshold, then abnormal sounds are prevented, but the device complexity increases
Solution Approach 1:
The compressor performs preliminary compression on the reference signal before it is processed by the adaptive filter. By pre-compressing the signal when its amplitude exceeds a threshold, the system prevents potential abnormal sounds from occurring in the first place, rather than correcting them afterward. This proactive approach resolves the contradiction by addressing the harmful effect at its source.
2Reliability
If the step size parameter is adjusted using the reference signal before compression, then noise reduction efficacy is optimized, but the device complexity increases
Solution Approach 1:
The μ adjuster implements a feedback mechanism that continuously monitors the reference signal and dynamically adjusts the step size parameter accordingly. By using the reference signal before compression as feedback input, the system optimizes the adaptive filter's performance in real-time, adapting to changing noise conditions. This feedback loop resolves the contradiction by maintaining high noise reduction efficacy through intelligent parameter adaptation.
3Reliability
If the adaptive filter coefficients are updated continuously, then noise reduction performance is maintained, but the processing time increases
Solution Approach 1:
The filter coefficient updater performs periodic updates of the adaptive filter coefficients at discrete time intervals rather than continuously. This periodic updating strategy maintains noise reduction performance by regularly refreshing the filter coefficients to adapt to changing acoustic conditions, while avoiding the excessive processing time that would result from continuous updates. The periodic action resolves the contradiction by finding an optimal update frequency.
Data Source
AI summary
An active noise reduction device reduces noise in a space in an automobile. The active noise reduction device includes: a reference signal input terminal that receives a reference signal outputted by a reference signal source and having a correlation with the noise, the reference signal source being attached to the automobile; a compressor that compresses and outputs the reference signal received by the reference signal input terminal and having an amplitude greater than or equal to a threshold; an adaptive filter unit that applies an adaptive filter to the reference signal outputted from the compressor to generate a canceling signal to be used to output a canceling sound for reducing the noise; and a filter coefficient updater that updates a coefficient of the adaptive filter.