Active Noise Control System With Echo Cancellation Adaptive Filter
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Solution Overview
Problem
Existing active noise control systems face challenges in effectively canceling noise when the output sound of a sound source device is input to a microphone, as it introduces disturbances that hinder the generation of appropriate noise-canceling sound.
Innovation Solution
An active noise control system is designed with an echo cancellation adaptive filter and a noise cancellation adaptive filter, which update their coefficients using the Filtered-X LMS algorithm and LMS algorithm respectively, to minimize errors caused by the output sound of the sound source device, thereby eliminating the influence of echoes and sound source device outputs on noise cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the output sound of a sound source device is input to a microphone for noise detection, then the system can utilize available audio signals for processing, but the output sound becomes a disturbance that hinders generation of appropriate noise-canceling sound
Solution Approach 1:
The patent segments the noise cancellation process into two independent adaptive filters: an echo cancellation adaptive filter that handles the sound source device output, and a noise cancellation adaptive filter that handles actual noise. This segmentation allows each filter to focus on its specific task without interference, resolving the contradiction between utilizing available signals and avoiding disturbances.
Solution Approach 2:
The patent introduces an intermediary processing stage where the output of the sound source device is separately processed through an echo cancellation adaptive filter before being combined with the noise cancellation path. This intermediary processing prevents the sound source output from directly interfering with the noise cancellation adaptive filter, while still allowing full utilization of the available audio signals.
2Device complexity
If the output of the second sound source device is used as input to the adaptive filter along with noise, then the system structure remains simple, but the output sound becomes a disturbance that hinders noise cancellation
Solution Approach 1:
The patent divides the single adaptive filter into two separate adaptive filters with distinct functions. The echo cancellation adaptive filter processes the sound source device output, while the noise cancellation adaptive filter processes the microphone input. This segmentation increases structural complexity but dramatically improves noise detection accuracy by eliminating the disturbance effect.
Solution Approach 2:
The patent introduces an intermediary echo cancellation stage that processes the sound source device output before it reaches the noise cancellation path. This intermediary processing separates the useful signal from the harmful disturbance, improving measurement precision while maintaining reasonable system complexity through modular design.
3Device complexity
If echo cancellation and noise cancellation are performed using a single adaptive filter, then the system configuration is simplified, but the filter cannot effectively distinguish between echo and noise components
Solution Approach 1:
The patent segments the cancellation function into two specialized adaptive filters: one dedicated to echo cancellation and another dedicated to noise cancellation. Each filter is optimized for its specific task, using appropriate reference signals and error signals. This segmentation enhances reliability by ensuring that each filter operates in its optimal performance regime without being compromised by the other function.
Solution Approach 2:
While the patent uses separate filters for different functions, each adaptive filter maintains universal adaptability through the LMS algorithm, allowing them to automatically adjust to different acoustic environments and signal characteristics. This combination of specialization and universal adaptability ensures high reliability across varying operating conditions.
Data Source
AI summary
A signal e(z) obtained by subtracting echo-canceling sound from an output of a second microphone is used as an error of an echo cancellation adaptive filter and a noise cancellation adaptive filter, and an output of a first sound source device is added to the signal e(z) and output from a first speaker. The echo cancellation adaptive filter generates echo-canceling sound from an addition signal of the output of the second sound source device and the output of the first microphone such that the signal e(z) is minimized. The noise cancellation adaptive filter generates the noise-canceling sound from the output of the first sound source device such that the signal e(z) is minimized, and outputs the noise-canceling sound from the second speaker.