Active Noise Control With Microphone Gain and Delay Matching
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Solution Overview
Problem
Existing active noise control systems face challenges in efficiently canceling noise when there is a significant difference in transfer functions, such as gain or delay time, between multiple error microphones due to the increased number of adaptive filters, leading to excessive processing load and inadequate noise cancellation.
Innovation Solution
An active noise control system with multiple error microphones that uses a gain adjustment section to balance the loudness levels and a delay adjustment section to synchronize the delay times of noise canceling sounds output from different speakers, based on the relative positions of the microphones, to effectively cancel noise despite varying transfer functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple adaptive filters are used to handle large differences in transfer functions between error microphones, then noise cancellation performance is improved, but processing load increases excessively
Solution Approach 1:
The patent combines multiple error microphone signals into a single summed error signal, reducing multiple adaptive filters to one. This merging approach maintains noise cancellation effectiveness while dramatically reducing processing load by eliminating redundant filter operations.
Solution Approach 2:
The single adaptive filter processes the summed error signal from multiple microphones, serving a universal function that replaces multiple specialized filters. This multi-functional approach allows one filter to handle noise cancellation for the entire array of microphones, reducing overall system complexity.
2Measurement precision
If multiple adaptive filters are used to account for different transfer functions, then noise cancellation accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple error microphone inputs into a single summed signal that feeds one adaptive filter, reducing system complexity while preserving cancellation accuracy through coherent signal combination that accounts for transfer function differences.
Solution Approach 2:
The patent changes the approach from multiple filters with different parameters to a single filter processing a summed signal, where the summation operation itself adapts to handle transfer function variations, effectively changing the system parameters to reduce complexity.
3Measurement precision
If error microphones are positioned at different locations to capture noise accurately, then noise detection precision is improved, but transfer function differences increase
Solution Approach 1:
The patent combines signals from multiple error microphones positioned at different locations into a single summed error signal, maintaining the spatial distribution benefits for noise detection while unifying the processing path to handle transfer function differences through the summation operation.
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 achieves effective noise cancellation even with large differences in transfer functions by optimizing the gain and delay adjustments, reducing the need for multiple adaptive filters and maintaining high cancellation performance.
Implementation Method 1
an active noise control system in which sound, such as music, output from a sound source apparatus 51 for a user in a first area to a speaker 52 for the user in the first area is determined as noise for a user in a second area and a noise canceling sound that is generated by an adaptive filter 53 is emitted from a speaker 54 in the second area
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
An active noise control system includes an error adder that generates an error signal by adding an output of a left-seat left microphone and an output of a left-seat right microphone, an adaptive filter that generates a noise canceling sound from a reference signal by performing an adaptive operation using the reference signal and the error signal, a left channel gain adjustment section that adjusts a gain of the noise canceling sound to be output to a left-seat left speaker, and a right channel gain adjustment section that adjusts a gain of the noise canceling sound to be output to the left-seat right speaker. A ratio between the gains of the left channel gain adjustment section and the right channel gain adjustment section matches a ratio between loudness levels of noise transmitted to the output of the left-seat left microphone and the output of the left-seat right microphone.