Active Noise Control Device Spatial Arrangement Optimization
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Solution Overview
Problem
Existing noise reduction devices in closed-structure bodies like aircraft and railway vehicles face challenges in effectively reducing noise over a wide frequency band due to causality constraints and correlation issues between noise detection and control, particularly with unfavorable positional relations between microphones and speakers.
Innovation Solution
A noise reduction device is configured with multiple noise detecting units and control-sound outputting units, where the number of units closer to the control center is minimized and those farther away are maximized, adhering to specific distance and wavelength criteria to ensure causality and correlation, allowing effective noise reduction across a wide frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If control-sound outputting units are disposed closer to the control center, then the noise reduction effect is improved, but the causality constraint is violated and correlation between noise detection and control deteriorates
Solution Approach 1:
The patent changes the spatial parameter (distance) of control-sound outputting units relative to the control center. By optimizing the distance to be greater than or equal to d0+t×v-λ/2, the system satisfies causality constraints while maintaining effective noise reduction across a wide frequency band.
Solution Approach 2:
The patent transitions from considering only the noise reduction effect in one dimension to simultaneously considering spatial arrangement, causality constraints, and correlation in multiple dimensions. This multi-dimensional optimization enables effective noise reduction while satisfying physical constraints.
2Difficulty of detecting and measuring
If control-sound outputting units are disposed farther from the control center, then the causality constraint is satisfied, but the noise reduction effect deteriorates
Solution Approach 1:
The patent optimizes the distance parameter of control-sound outputting units to a specific range (≥ d0+t×v-λ/2) that simultaneously satisfies causality constraints and maintains effective noise reduction. This parameter optimization resolves the trade-off between the two conflicting requirements.
3Reliability
If the number of control-sound outputting units is increased, then the noise reduction coverage is improved, but the device complexity and processing cost increase
Solution Approach 1:
The patent reduces the number of control-sound outputting units by optimizing their spatial arrangement and distance from the control center. This parameter optimization enables effective noise reduction with fewer units, thereby reducing device complexity and processing cost.
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 achieves enhanced noise reduction across a wide frequency band from lower to higher frequencies, even with multiple noise sources and varied noise directions, while reducing the complexity and cost of control-signal processing.
Implementation Method 1
generates a control-sound signal to reduce, at a control center of a control space, the noise
Implementation Method 2
outputs a sound based on the control sound signal
Data Source
AI summary
A noise reduction device includes a plurality of noise microphones, noise controller, and control speakers. Noise controller generates a control-sound signal to reduce a noise, at a control center of a control space, with the noise being detected by the plurality of noise microphones. Noise microphone disposed at a shorter distance from the control center than distance “d” indicated by Relational Expression (1) is smaller in number than noise microphones disposed at longer distances than distance “d” where “λ” is a wavelength corresponding to control upper-limit frequency “f” in noise microphones, “d0” is a distance from the control center to control speakers, “t” is a control delay time in control speakers, and “v” is a sound speed.d=d0+t×v−λ/2 (1)