Noise Controller with Effect Measuring Unit for Target Noise Isolation
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Solution Overview
Problem
Conventional noise control techniques struggle to accurately reduce specific noises in multi-occupant spaces, such as cars or airplanes, due to interference from non-target noises, leading to incomplete noise cancellation.
Innovation Solution
A noise controller system that includes a noise detector, control filter, speaker, error microphone, transmission characteristics correction filter, factor updater, and effect measuring unit, which processes signals to isolate and minimize residual noise, allowing for precise noise reduction at control points without affecting non-target noises.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional noise control techniques are applied in multi-occupant spaces, then noise reduction at control points is attempted, but non-target noises (e.g., audio playback) are incorrectly included in the control target, reducing measurement precision and control accuracy
Solution Approach 1:
The patent segments the noise control process into two distinct measurement modes: control-on measurement (when noise control is active) and control-off measurement (when noise control is inactive). This segmentation allows the system to separately evaluate the noise reduction effect only on target noises while excluding non-target noises from the measurement, thereby improving measurement precision without losing information about different noise types.
Solution Approach 2:
The patent introduces an intermediary mechanism by using the control filter's output signal as a reference for control-off measurement. This intermediary signal represents what the noise would be without active control, allowing comparison with the actual controlled noise (control-on) to isolate and measure only the effect on target noises, preventing contamination from non-target noises like audio playback.
2Reliability
If the error microphone collects all noises at the control point, then comprehensive noise detection is achieved, but the control system cannot distinguish between target noises to be reduced and non-target noises, leading to inaccurate noise reduction
Solution Approach 1:
The patent applies local quality by making the measurement process context-dependent. The control-off measurement uses the control filter's output signal (local to the control system) as the reference, while the control-on measurement uses the actual error microphone signal. This local differentiation ensures that only target noises passing through the control system are measured for reduction effectiveness, excluding non-target noises from the reliability calculation.
Solution Approach 2:
The patent implements feedback by continuously monitoring the error signal and comparing it with the control filter's output signal. The factor updater uses this feedback to adjust control factors, and the effect measuring unit uses feedback from both control-on and control-off measurements to accurately evaluate noise reduction effectiveness. This feedback mechanism ensures that only target noises are considered in the reliability assessment.
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 system effectively measures and reduces noise at control points by distinguishing between noise subjected to control and noise not subjected to control, ensuring accurate noise reduction without interference from non-target sounds.
Implementation Method 1
an error microphone that is disposed at a control point where interference between the noise propagated from the noise source and the control sound reproduced by the speaker occurs, and detects a residual noise that is left at the control point as a result of the interference
Data Source
AI summary
A noise controller includes: a noise detector; a control filter that performs signal processing on a noise signal using a control factor; a speaker that reproduces an output signal from the control filter; an error microphone that detects a residual noise at a control point; a transmission characteristics correction filter that performs signal processing on the noise signal, using characteristics of sound transmission from the speaker to the error microphone; a factor updater that updates the control factor; a correction filter that performs signal processing on an output signal from the control filter, using the characteristics of sound transmission; a subtractor that subtracts, from an error signal indicative of the residue noise, an output signal from the correction filter; and an effect measuring unit that measures a noise reduction effect at the control point based on a difference between an output signal from the subtractor and the error signal.