Active Noise Reduction System Using Microphone Signal Separation

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Solution Overview

Problem

Conventional active noise reduction systems are expensive due to the use of acceleration sensors for generating noise signals, which increases the overall cost and complexity.

Innovation Solution

An active noise reduction system that uses multiple noise microphones to generate reference and error signals, allowing for the removal of canceling sound components and enabling effective noise reduction without the need for expensive sensors, and employs adaptive filters to generate control signals for canceling sound output devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If an acceleration sensor is used to generate the noise signal, then the noise signal can be obtained, but the system cost increases

Engineering Contradiction:

Improvenoise signal acquisitionVSAvoidsystem cost

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces expensive acceleration sensors with inexpensive microphones to acquire noise signals. The microphones are standard, low-cost components that can effectively capture acoustic noise without requiring the complex and costly acceleration sensing technology, thus resolving the contradiction between measurement capability and system cost.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent substitutes mechanical vibration sensing (acceleration sensors) with acoustic field sensing (microphones). Instead of mechanically detecting noise vibrations, the system uses microphones to capture acoustic pressure variations, replacing a mechanical sensing approach with an acoustic field-based approach that is more cost-effective.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If the canceling sound component is present in the reference signal, then the adaptive filter cannot converge properly, but removing it increases processing complexity

Engineering Contradiction:

Improveadaptive filter convergenceVSAvoidsignal processing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies preliminary echo cancellation to remove the canceling sound component from the reference signal before the adaptive filter processes it. By pre-removing the echo of the canceling sound from the microphone input, the reference signal becomes clean and free of self-interference, enabling proper adaptive filter convergence without requiring complex iterative removal processes.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary processing stage that separates the canceling sound generation path from the reference signal path. The reference signal is derived from the original noise input before it is processed by the adaptive filter, acting as an intermediary that prevents the canceling sound echo from contaminating the reference signal, thus simplifying the overall processing while ensuring reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

This approach results in a cost-effective active noise reduction system capable of effectively reducing noise across a wide frequency band, with reduced computational load and minimal impact on audio quality, allowing for easy integration into existing vehicles and portable devices.

Implementation Method 1

a plurality of noise microphones (13A-13E) configured to generate a plurality of noise signals based on the noise

Methodology Applied

Scientific EffectAcoustic detection and transduction:

Implementation Method 2

a canceling sound output device (12A-12D) configured to output a canceling sound for canceling a noise

Methodology Applied

Scientific EffectElectroacoustic transduction:

Implementation Method 3

generate a correction reference signal by removing a component of the canceling sound from the reference signal

Methodology Applied

Scientific EffectSignal processing and subtraction:

Implementation Method 4

reduce a noise by causing a canceling sound in an opposite phase to the noise to interfere with the noise

Methodology Applied

Scientific EffectAcoustic interference: Interference

Data Source

PatentUS12254861B2Active noise reduction system, active noise reduction method, and non-transitory computer-readable storage medium

Publication Date: 2025.03.18 HONDA MOTOR CO LTD

AI summary

An active noise reduction system includes a canceling sound output device configured to output a canceling sound, a plurality of noise microphones configured to generate a plurality of noise signals based on a noise, and a controller configured to control the canceling sound output device based on the plurality of noise signals, wherein the controller is configured to acquire the plurality of noise signals output from the plurality of noise microphones, select a reference signal and an error signal from among the plurality of noise signals, the reference signal corresponding to the noise, the error signal corresponding to an error between the noise and the canceling sound, generate a correction reference signal by removing a component of the canceling sound from the reference signal, and generate a control signal based on the correction reference signal, the control signal being a signal for controlling the canceling sound output device.