Active Noise Control Processing for Stable Vehicle Noise Reduction

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Solution Overview

Problem

Existing active noise control devices face delays and instability in noise reduction operations due to varying processing times and mismatched acoustic transfer characteristics, leading to decreased noise reduction effectiveness.

Innovation Solution

The active noise control device employs a first signal processor operating in cycle T1 and a second signal processor operating in cycle T2, with a sample rate converter upsampling the adaptive filter coefficient, to synchronize the cancellation sound output and reduce latency, while using simulated transfer characteristics to optimize the adaptive filter coefficient.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the adaptive filter coefficient is updated frequently to improve noise reduction effectiveness, then the noise reduction performance is improved, but the processing time varies and causes delay and instability

Engineering Contradiction:

Improvenoise reduction effectivenessVSAvoidprocessing time variation

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent divides the signal processing into two separate processors: a first signal processor that operates at a higher frequency cycle T1 for real-time noise reduction, and a second signal processor that operates at a lower frequency cycle T2 for adaptive filter coefficient updates. This segmentation allows each processor to optimize its operation independently, with the second processor updating coefficients less frequently to avoid processing time variations affecting real-time performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements periodic action by operating the first signal processor at cycle T1 and the second signal processor at cycle T2, where T2 is longer than T1. The sample rate converter ensures synchronization between these periodic operations, allowing the system to maintain stable noise reduction performance while reducing the frequency of coefficient updates to minimize processing time variations.

Inventive Principle:

Principle #19Periodic action

2Reliability

If the adaptive filter coefficient is updated frequently to improve noise reduction effectiveness, then the noise reduction performance is improved, but the delay increases and stability decreases

Engineering Contradiction:

Improvenoise reduction effectivenessVSAvoiddelay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies preliminary action by pre-calculating and storing the adaptive filter coefficient updates in advance. The second signal processor prepares coefficient updates during its longer cycle T2, and the sample rate converter ensures these pre-prepared updates are synchronized with the first signal processor's operations at cycle T1, reducing real-time delay.

Inventive Principle:

Principle #10Preliminary action

3Speed

If the processing cycle is shortened to reduce latency, then the response speed is improved, but the processing time variation increases causing instability

Engineering Contradiction:

Improveresponse speedVSAvoidprocessing time variation

Core Design Contradiction:

SpeedVSLoss of time

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies parameter changes by adjusting the operating frequencies of the two signal processors to different cycles T1 and T2. The first processor uses a shorter cycle T1 for fast response, while the second processor uses a longer cycle T2 for stable coefficient updates. The sample rate converter synchronizes these different parameters to maintain system stability.

Inventive Principle:

Principle #35Parameter changes

4Stability of the object's composition

If the adaptive filter coefficient is updated less frequently to reduce processing time variation, then the stability is improved, but the noise reduction effectiveness decreases

Engineering Contradiction:

Improveprocessing stabilityVSAvoidnoise reduction effectiveness

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent ensures continuity of useful action by maintaining continuous operation of the first signal processor at cycle T1 for real-time noise reduction, while the second signal processor continuously updates coefficients at cycle T2. The sample rate converter ensures continuous synchronization between the two processors, maintaining stable and effective noise reduction performance.

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS20250336387A1Active noise control device, vehicle, and active noise control method

Publication Date: 2025.10.30 PANASONIC AUTOMOTIVE SYST CO LTD

AI summary

An active noise control device includes: a first signal processor that generates a cancellation signal for outputting a cancellation sound for reducing noise in a space inside an automobile, by applying an adaptive filter to a reference signal correlating with the noise; a second signal processor that updates a coefficient of the adaptive filter; and a sample rate converter. The first signal processor operates in cycle T1, the second signal processor operates in cycle T2 that is longer than cycle T1, and the sample rate converter upsamples the coefficient of the adaptive filter updated by the second signal processor and outputs the coefficient upsampled to the first signal processor. Cycle T1 is longer than a difference between maximum and minimum values of a processing time required from when the second signal processor obtains the reference signal to when the second signal processor updates the coefficient of the adaptive filter.