Acoustic Signal Processing for Active Noise Cancellation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional active noise cancellation (ANC) systems face performance degradation due to localized noise, such as wind noise, which is detected by the reference microphone but not the error microphone, leading to incorrect anti-noise generation and increased acoustic noise in the output.

Innovation Solution

An acoustic signal processing system that classifies the relationship between ambient and localized noise components, using a classifier to determine a classification value representing their relative volumes, and processes the sound signal accordingly to adjust the cutoff frequency of a high pass filter, thereby modifying the noise components and improving ANC system performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the reference microphone is positioned to detect ambient noise, then ambient noise detection is improved, but localized noise such as wind noise is also detected causing performance degradation

Engineering Contradiction:

Improveambient noise detection accuracyVSAvoidANC system performance

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent segments the noise signal into two distinct components: ambient noise (detected by reference microphone) and localized noise (detected by error microphone). By separating these noise sources into different detection channels, the system can process each type of noise differently, preventing localized noise from degrading ANC performance while maintaining ambient noise detection capability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The error microphone acts as an intermediary device that detects localized noise components. Its output is fed to the localized noise canceller, which generates anti-localized-noise signals to counteract the harmful localized noise detected by the error microphone, thereby protecting the overall ANC system from performance degradation

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If high pass filtering is applied to remove localized noise, then localized noise attenuation is improved, but ambient noise cancellation performance may be affected

Engineering Contradiction:

Improvelocalized noise attenuationVSAvoidambient noise cancellation

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent implements separate processing paths for ambient noise and localized noise. The high pass filter operates only on the error microphone signal to remove localized noise components, while the ambient noise cancellation path processes the reference microphone signal independently. This segmentation allows localized noise attenuation without compromising ambient noise cancellation performance

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different filtering characteristics are applied to different signal paths based on their specific requirements. The error microphone path receives high pass filtering to eliminate localized noise, while the reference microphone path maintains full frequency response for accurate ambient noise detection. Each path has optimized local processing characteristics suited to its function

Inventive Principle:

Principle #3Local quality

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 attenuates localized noise, enhancing ANC performance by dynamically adjusting the high pass filter cutoff frequency, thereby reducing unwanted noise components and improving the overall noise cancellation effect.

Implementation Method 1

The reference microphone 104 detects the ambient noise A(z) and localized noise LN(z)

Methodology Applied

Scientific EffectMicrophone transduction:

Implementation Method 2

The speaker 108 converts the speaker drive signal D(z) into the speaker sound SPKR(z)

Methodology Applied

Scientific EffectSpeaker transduction:

Implementation Method 3

ANC is also commonly referred to as active noise reduction or active noise control. The ANC system actively generates 'anti-noise' acoustic pressure waves to destructively interfere with the noise acoustic waves, which, thus, cancel the noise acoustic waves

Methodology Applied

Scientific EffectDestructive interference: Interference

Data Source

PatentUS11863948B1Sound components relationship classification and responsive signal processing in an acoustic signal processing system

Publication Date: 2024.01.02 CIRRUS LOGIC INT SEMICON LTD

AI summary

An acoustic signal processing system and method includes classification technology to classify a relationship between at least two sound components of a received sound signal. The exemplary sound components are ambient noise and localized noise. The classification technology dynamically determines a classification value that represents the relationship between the sound components and processes the sound signal in accordance with the acoustic signal classification to modify the sound signal. In at least one embodiment, dynamic classification of the relationship between sound components in a sound signal and responsive signal processing improve performance of systems, such as an active noise cancellation (ANC) system, by, for example, attenuating at least one of the sound components and/or enhancing at least one of the sound components. In an ANC system context, the sound components generally include noise components such as ambient noise and noise localized to a microphone.