Active Noise Control System Using Independent Component Analysis
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Solution Overview
Problem
Existing active noise control systems face challenges in effectively canceling noise in the high frequency range, particularly in feedforward systems that require sensors to detect noise-correlating events upstream of the target position, and in feedback systems where delay in the feedback loop hampers high-frequency noise cancellation.
Innovation Solution
An active noise control system that employs a blind configuration without a sensor for detecting noise-correlating events, using a microphone to collect sound data, an adaptive filter, and storage to separate and store a noise component as a pseudo noise signal. This pseudo noise signal is then used as input for the adaptive filter to generate a noise cancellation sound, thereby overcoming the limitations of traditional feedforward and feedback systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedforward active noise control uses a sensor to detect noise-correlating events upstream of the target position, then noise cancellation can be achieved, but the system becomes complex and requires additional sensors that may not be feasible in all configurations
Solution Approach 1:
The patent extracts only the necessary noise information directly from the error signal (microphone output) through noise separation processing, rather than requiring external sensors to detect noise-correlating events. This extraction approach obtains the needed reference signal without adding system complexity or requiring additional sensors upstream of the target position.
Solution Approach 2:
The system uses the error signal itself (from the microphone near the target position) as the source for noise separation, making the system self-sufficient. The error signal contains both the residual noise and the noise cancellation sound, and through noise separation processing, the reference signal is derived from this self-contained source without needing external sensors.
2Device complexity
If feedback active noise control is used to simplify system configuration, then sensor requirements are reduced, but delay in the feedback loop hampers high-frequency noise cancellation
Solution Approach 1:
The patent performs noise separation processing to extract the reference signal from the error signal before it is fully processed through the feedback loop. By obtaining the reference signal through noise separation of the monitored error signal, the system reduces the effective delay in the control path, enabling better high-frequency noise cancellation while maintaining the simplicity of feedback configuration.
3Measurement precision
If the microphone is placed near the target position to accurately measure the error signal, then noise cancellation accuracy improves, but the computational time becomes insufficient for high-frequency noise cancellation in feedforward systems
Solution Approach 1:
The patent replaces the traditional mechanical/sensor-based approach of detecting noise-correlating events upstream with a signal processing approach. By using noise separation processing on the error signal, the system substitutes physical sensor placement and upstream detection with computational methods that work directly with the monitored error signal, achieving accurate noise cancellation without the time loss associated with upstream sensor detection and signal propagation.
Data Source
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AI summary
An active noise control system includes circuitry configured to perform independent component analysis when a level of a sound output from a microphone becomes greater than a predetermined level. In an independent component analysis process, by the independent component analysis, the circuitry separates a noise component from monitoring sound data that is output from the microphone, and stores data representing the noise component as statistical noise data. An adaptive filter in the active noise control system performs an adaptive operation to adapt an output of the microphone as an error, and outputs, as a noise cancellation sound from a speaker, a sound represented by noise cancellation sound data that is obtained by filtering the stored statistical noise data. The adaptive filter adapts, as an error, a filter coefficient used in filtering the monitoring sound data output from the microphone.