Active Noise Canceller Stability Control for Changing Secondary Paths
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Solution Overview
Problem
Existing active noise canceller devices face instability due to changes in secondary path transmission characteristics, leading to noise amplification and abnormal sounds, particularly in vehicle environments where factors like air conditioning can disrupt control stability.
Innovation Solution
An active noise canceller device that includes a control device with a stability judgment part to detect and address instability by adaptively updating filters based on noise signals, using a control filter, primary and secondary path filters, and a stability judgment mechanism to maintain stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the adaptive filter is updated based on measured transmission characteristics, then the noise reduction effect is improved, but the system becomes unstable when transmission characteristics change
Solution Approach 1:
The patent implements a stability judgment mechanism that continuously monitors the adaptive filter coefficients and transmission characteristics. When instability is detected through feedback from the stability judgment part, the system adjusts or resets the adaptive filter to maintain control stability while preserving noise reduction effectiveness.
Solution Approach 2:
The system dynamically adapts by continuously updating the adaptive filter based on changing transmission characteristics while incorporating stability judgment. This allows the system to maintain optimal noise reduction performance under varying conditions (such as air conditioner operation) without sacrificing control stability.
2Measurement precision
If the transmission characteristics are corrected using predetermined correction values, then the control accuracy is improved, but noise amplification and abnormal sounds occur when characteristics change
Solution Approach 1:
The stability judgment part provides continuous feedback on system stability by monitoring filter coefficients and transmission characteristics. When noise amplification or abnormal sounds are detected, the feedback mechanism triggers corrective actions such as resetting or adjusting the adaptive filter, thereby eliminating harmful effects while maintaining control accuracy.
Solution Approach 2:
The system performs self-diagnosis and self-correction through the stability judgment mechanism. When instability or abnormal conditions are detected, the system automatically adjusts its own parameters and filter coefficients without external intervention, eliminating noise amplification and abnormal sounds while preserving measurement precision.
3Ease of operation
If environmental factors like air conditioner are controlled, then the comfort is improved, but the noise cancellation stability deteriorates
Solution Approach 1:
The system dynamically adapts to environmental changes caused by air conditioner operation. The stability judgment mechanism continuously monitors for changes in transmission characteristics induced by air flow or temperature changes, and automatically adjusts the adaptive filter to maintain cancellation sound stability while allowing comfortable environmental control.
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 device effectively maintains noise reduction by accurately detecting and correcting instability, ensuring stable cancellation sound output without producing unpleasant sounds.
Implementation Method 1
an error microphone that detects the synthetic sound of the noise and the cancellation sound and outputs the synthetic sound signal
Implementation Method 2
an active noise canceller device is known which reduces noise by causing cancellation sound which are opposite in phase to the noise to interfere with the noise
Data Source
AI summary
An active noise canceller device includes: a cancellation sound output device, outputting a cancellation sound for a noise; noise microphones, generating noise signals; a control device, controlling the cancellation sound output device based on the noise signals. The control device executes: obtaining noise signals, selecting reference signals corresponding to the noise and an error signal corresponding to an error of the noise and the cancellation sound from the noise signals, generating a correction reference signal, and generating a control signal. The control device includes: a control filter, generating the control signal of the control device; a primary path filter, generating a noise estimation signal from the reference signals; a secondary path filter, generating a cancellation sound estimation signal from the correction reference signal; and a stability judgment part, judging a stability of the cancellation sound from the control filter, the primary path filter, and the secondary path filter.