Active Noise Control Filter Coefficient Generation for Speaker Distortion

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Solution Overview

Problem

Active noise control systems face performance degradation due to the inability of speakers to reproduce signals outside their frequency specifications, leading to distortion and reduced noise elimination effectiveness.

Innovation Solution

An elimination filter coefficient generation method that includes route filtering, noise signal generation with specific frequency characteristics, and addition of noise signals to the reference signal, ensuring the elimination filter coefficient does not exceed the speaker's reproduction capabilities, thereby preventing distortion and maintaining noise elimination performance across all frequency bands.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an elimination filter coefficient is generated by using an adaptive algorithm without taking frequency characteristics of a speaker into consideration, then noise elimination performance may improve in theory, but distortion occurs and noise elimination performance degrades in practice

Engineering Contradiction:

Improvenoise elimination performanceVSAvoiddistortion

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent modifies the reference signal by adding noise signals with specific frequency characteristics before generating the elimination filter coefficient. This parameter change ensures that the generated coefficient does not cause the speaker to reproduce signals outside its frequency capabilities, thereby preventing distortion while maintaining noise elimination performance.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces a noise signal as an intermediary element. By adding this noise signal with predetermined frequency characteristics to the reference signal, it acts as a mediator that guides the adaptive algorithm to generate elimination filter coefficients that are compatible with the speaker's frequency reproduction capabilities, thus avoiding distortion.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If large signals are input in frequency bands outside the speaker's reproduction range, then the adaptive algorithm can learn effectively, but the speaker cannot reproduce the sound and distortion occurs

Engineering Contradiction:

Improveadaptive algorithm learning efficiencyVSAvoidnoise elimination performance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent changes the frequency distribution parameters of the input signal by superimposing a noise signal with specific frequency characteristics on the reference signal. This ensures that the adaptive algorithm learns effectively from signals that are within the speaker's reproduction capabilities, preventing distortion while maintaining learning efficiency.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent performs preliminary processing on the reference signal by adding a noise signal before the adaptive algorithm generates the elimination filter coefficient. This preliminary action shapes the frequency characteristics of the input signal to match the speaker's capabilities, preventing future distortion issues.

Inventive Principle:

Principle #10Preliminary action

3Device complexity

If the elimination filter coefficient is generated without considering speaker frequency characteristics, then the system is simpler, but noise elimination performance degrades due to distortion

Engineering Contradiction:

Improvefilter coefficient generation processVSAvoidnoise elimination performance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent modifies the reference signal parameters by adding a noise signal with specific frequency characteristics. This simple parameter change guides the adaptive algorithm to generate elimination filter coefficients that are compatible with speaker frequency capabilities, improving noise elimination performance without significantly increasing system complexity.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12002445B2Cancel filter coefficient generation method, cancel filter coefficient generation apparatus, and program

Publication Date: 2024.06.04 NIPPON TELEGRAPH & TELEPHONE CORP

AI summary

Provided is a technology for generating an elimination filter coefficient for suppressing degradation of noise elimination performance. An elimination filter coefficient generation method for inputting a reference signal output from a reference microphone for collecting noise and an error signal output from an error microphone for collecting sound at a position that needs to be silent, and generating an elimination filter coefficient used for filtering for generating an elimination signal for eliminating noise at the position that needs to be silent from the reference signal includes: a route filtering step for generating a filtered reference signal from the reference signal by filtering using a route filter coefficient indicating acoustic characteristics of a route from a speaker for emitting sound based on the elimination signal to the error microphone; a first noise signal generation step for generating a predetermined signal as a first noise signal; a noise signal addition step for generating an added reference signal from the filtered reference signal and the first noise signal; and an elimination filter coefficient generation step for generating the elimination filter coefficient from the error signal and the added reference signal.