Active Noise Cancellation Filter for Wider Vehicle Quiet Zones
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Solution Overview
Problem
Existing active noise canceller devices have limited sound reduction ranges, which are further constrained by higher frequencies, and increasing the number of microphones to expand this range increases hardware costs and complexity.
Innovation Solution
An active noise canceller device that includes a reference signal generation, cancellation sound output, error detection, and control system, with components like a reference signal correction part, noise estimation, and control filter, allowing for expanded sound reduction range without additional microphones, and adjusts the control range based on occupant position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the number of control microphones is increased to expand the sound reduction range, then the sound reduction range is expanded, but the hardware settings become larger and cost increases
Solution Approach 1:
The patent creates virtual microphones by processing signals from existing microphones through coordinate transformations and acoustic transfer function calculations. Instead of physically placing microphones at multiple positions, the system mathematically generates equivalent signals that would be obtained from virtual microphone positions, thereby expanding the control range without adding hardware.
Solution Approach 2:
The patent replaces the mechanical approach of adding more physical microphones with a signal processing approach. By using coordinate transformations and acoustic transfer function estimations, the system substitutes physical hardware expansion with computational methods to achieve the same effect of expanding sound reduction coverage.
2Measurement precision
If the frequency is increased, then the noise cancellation precision is improved, but the sound reduction range becomes narrower
Solution Approach 1:
The patent addresses the frequency-range tradeoff by introducing spatial dimensionality through coordinate transformations. By estimating acoustic transfer functions between multiple virtual microphone positions and the speaker, the system creates a three-dimensional sound reduction coverage that maintains effectiveness across different frequencies and spatial locations, overcoming the limitation where higher frequencies normally produce narrower reduction ranges.
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 expands the sound reduction range and maintains consistent noise cancellation across varying positions within a vehicle, improving the habitability of transportation systems without increasing hardware costs.
Implementation Method 1
a speaker that outputs cancellation sound (to cancel noise)
Implementation Method 2
a microphone that outputs an error signal and generates a control signal based on the error signal
Data Source
AI summary
An active noise canceller device includes: a reference signal generation device, generating a reference signal corresponding to a noise; a cancellation sound output device, outputting cancellation sound for canceling the noise; an error detection device, detecting an error between the noise and the cancellation sound and generating an error signal corresponding to the error; and a control device, controlling the cancellation sound output device that further including: a reference signal correction part, correcting the reference signal; a noise estimation part, estimating a sound pressure; a sound pressure estimation part, estimating the sound pressure within an object range of the cancellation sound that cancels the noise; and a control filter, controlling the cancellation sound. The active noise canceller device updates the control filter based on the reference signal corrected by the reference signal correction part and a sound pressure estimated value of the sound pressure estimation part.