Adaptive Noise Cancellation with Secondary Path Estimation
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Solution Overview
Problem
Active noise control systems face challenges in improving adaptation speed and quality due to variations in the secondary path transmission function, leading to instability and reduced performance, especially in dynamic environments like motor vehicles.
Innovation Solution
An active noise cancellation system that includes an adaptive filter, a signal source, an acoustic actuator, a microphone, and an estimation unit, which estimates the transfer characteristic of the secondary path system using a measurement signal and a microphone signal to dynamically adjust filter coefficients and improve noise suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adaptive filter coefficients are modified to reduce error signal power, then noise suppression performance is improved, but system stability deteriorates due to variations in secondary path transmission function
Solution Approach 1:
The patent implements a feedback mechanism where the actual secondary path transmission function is continuously estimated from microphone signals and compensation signal outputs. This estimated transmission function is fed back to adjust the adaptive filter coefficients, creating a closed-loop system that maintains stability while improving noise suppression performance under varying conditions.
Solution Approach 2:
The patent introduces dynamic adaptation of the secondary path transmission function estimation. Instead of using a fixed model, the system continuously updates the transmission function characteristics based on real-time measurements from the microphone and compensation signal, allowing the system to adapt to changing acoustic conditions while maintaining stable operation.
2Measurement precision
If secondary path transmission function variations are compensated, then adaptation quality is improved, but device complexity increases
Solution Approach 1:
The patent employs self-service by having the system automatically estimate and compensate for secondary path variations using its own internal signals (microphone output and compensation signal). The system uses its own components to monitor and adjust itself, eliminating the need for external calibration equipment or complex manual configuration while maintaining high adaptation quality.
Solution Approach 2:
The patent replaces complex mechanical or physical calibration methods with digital signal processing techniques. Instead of physically measuring and adjusting the secondary path, the system uses mathematical models and algorithms to estimate and compensate for transmission function variations, simplifying the overall system while improving adaptation precision.
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
Enhances the speed and quality of noise adaptation, stabilizes the system, and effectively suppresses noise even in changing ambient conditions, improving music reproduction and speech intelligibility.
Implementation Method 1
The acoustic actuator radiates the compensation signal and the measurement signal to the listening position
Implementation Method 2
The microphone receives a first signal that is a superposition of the radiated compensation signal, the radiated measurement signal, and the noise signal at the listening position
Implementation Method 3
The adaptive filter receives a reference signal representing noise, and provides a compensation signal in response to the received reference signal
Implementation Method 4
The estimation unit estimates a transfer characteristic of the secondary path system in response to the measurement signal and the microphone signal
Data Source
AI summary
An active noise cancellation system includes an adaptive filter, a signal source, an acoustic actuator, a microphone, a secondary path and an estimation unit. The adaptive filter receives a reference signal representing noise, and provides a compensation signal in response to the received reference signal. The signal source provides a measurement signal. The acoustic actuator radiates the compensation signal and the measurement signal to the listening position. The microphone receives a first signal that is a superposition of the radiated compensation signal, the radiated measurement signal, and the noise signal at the listening position, and provides a microphone signal in response to the received first signal. The secondary path includes a secondary path system that represents a signal transmission path between an output of the adaptive filter and an output of the microphone. The estimation unit estimates a transfer characteristic of the secondary path system in response to the measurement signal and the microphone signal.