Active Noise Control with Combined Error Signals and Gain Matching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing active noise control systems face increased complexity and processing load due to the need for multiple adaptive filters when canceling noise for users in different seats, especially when there are significant differences in transfer functions between noise sources and microphones, leading to inadequate noise cancellation.
Innovation Solution
An active noise control system with a reduced number of adaptive filters uses multiple error microphones to generate a combined error signal, adjusting gain and delay to match noise source characteristics, ensuring effective noise cancellation despite varying transfer functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple adaptive filters are provided for each combination of speakers and error microphones to cancel noise for users in different seats, then noise cancellation performance is improved, but device complexity and processing load increase excessively
Solution Approach 1:
The patent combines the outputs of multiple error microphones (first error microphone and second error microphone) into a single monaural error signal. This merging approach allows one adaptive filter to process noise cancellation for multiple speakers and microphones simultaneously, reducing the total number of adaptive filters needed while maintaining effective noise cancellation performance for users in different seats
Solution Approach 2:
A single adaptive filter is designed to perform noise cancellation for multiple speaker-microphone combinations universally. The adaptive filter processes the combined monaural error signal and generates noise canceling sounds that are distributed to multiple speakers, enabling one filter to serve multiple functions across different user positions and audio channels
2Device complexity
If the same noise canceling sound is output from left and right speakers using a monaural error signal, then device complexity is reduced, but noise cancellation effectiveness deteriorates when transfer function differences are large
Solution Approach 1:
The patent applies different gain values to the noise canceling sound when outputting it to different speakers (first speaker and second speaker). By adjusting the gain for each speaker based on the transfer function characteristics specific to each speaker-microphone path, the system maintains effective noise cancellation for each local position even though a single adaptive filter is used for the entire system
Solution Approach 2:
The system changes the gain parameter of the noise canceling sound dynamically or statically for different speakers. The gain adjustment section modifies the amplitude of the noise canceling sound according to the transfer function differences between speakers and error microphones, ensuring optimal noise cancellation effectiveness for each speaker position while using a single adaptive filter
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 cancels noise by matching gain and delay adjustments to noise source conditions, providing efficient noise reduction with a simpler configuration.
Implementation Method 1
a first microphone (16L) that is disposed in a position displaced in a first direction relative to a user, a second microphone (16R) that is disposed in a position displaced in a second direction relative to the user
Implementation Method 2
an adaptive filter (183) configured to perform an adaptive operation of minimizing an error using a signal correlated with the noise as a reference signal and the addition signal as the error so as to generate a noise canceling sound
Implementation Method 3
a first speaker (12L) configured to emit sound toward an area around the position where the first microphone (16L) is disposed, a second speaker (12R) configured to emit sound toward an area around the position where the second microphone (16R) is disposed
Implementation Method 4
a gain adjustment section (184, 186) configured to adjust a ratio between a loudness level of a first noise canceling sound which is the noise canceling sound to be output to the first speaker (12L) and a loudness level of a second noise canceling sound which is the noise canceling sound to be output to the second speaker (12R)
Implementation Method 5
a delay adjustment section (185, 187) configured to adjust a delay time between a first noise canceling sound which is the noise canceling sound output to the first speaker (12L) and a second noise canceling sound which is the noise canceling sound output to the second speaker (12R)
Data Source
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.