Feed-Forward Adaptive Noise-Canceling Filter Selection

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Solution Overview

Problem

Adaptive noise-canceling systems for personal audio devices face challenges in effectively adapting to changes in acoustic environments and earpiece fit, leading to power consumption and complexity issues, with existing solutions introducing latency and instability.

Innovation Solution

An adaptive noise-canceling system using a feed-forward filter with a classifier and controller to select coefficients from a look-up table based on acoustic environment measurements, allowing for efficient noise cancellation with reduced power consumption and complexity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If complex adaptive noise-canceling circuits are used to adapt to environmental changes, then noise-canceling effectiveness is improved, but power consumption increases and system complexity increases

Engineering Contradiction:

Improvenoise-canceling effectivenessVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The system dynamically switches between different filter types (FIR and IIR) based on the acoustic environment detected by the classifier. In stable environments, IIR filters provide low power consumption. In changing environments, FIR filters provide adaptive noise canceling. This dynamic adaptation resolves the contradiction between effectiveness and power consumption.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The noise-canceling system is divided into separate functional modules: measurement subsystem, classifier, controller, and multiple filter types. This segmentation allows independent optimization of each module, enabling the system to achieve effective adaptation while managing overall complexity and power consumption through specialized subsystems.

Inventive Principle:

Principle #1Segmentation

2Reliability

If complex filtering and feedback systems are used to adapt to environmental changes, then noise-canceling effectiveness is improved, but latency increases

Engineering Contradiction:

Improvenoise-canceling effectivenessVSAvoidlatency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system dynamically selects between FIR and IIR filters based on environmental conditions. IIR filters provide lower latency for real-time noise canceling, while FIR filters are used when adaptation is needed. The controller switches between these filter types to maintain minimal latency while preserving adaptability, resolving the contradiction between effectiveness and latency.

Inventive Principle:

Principle #15Dynamics

3Use of energy by moving object

If IIR filters are used to reduce power consumption and complexity, then power consumption is reduced, but stability decreases due to coefficient variations

Engineering Contradiction:

Improvepower consumptionVSAvoidsystem stability

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

The system dynamically switches between IIR and FIR filters based on environmental stability detected by the classifier. When the acoustic environment is stable, IIR filters are used for low power consumption. When environmental changes are detected, the system switches to FIR filters which are more stable for adaptive filtering, thus resolving the contradiction between power consumption and stability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The measurement subsystem continuously monitors the acoustic environment and provides feedback to the controller. The controller uses this feedback to determine when to switch between filter types, ensuring that IIR filters are only used when stability conditions are met, thereby maintaining system stability while achieving low power consumption.

Inventive Principle:

Principle #23Feedback

4Adaptability or versatility

If the system adapts to both ambient noise and earspeaker fit changes, then adaptability is improved, but device complexity increases

Engineering Contradiction:

Improveenvironmental adaptationVSAvoidsystem complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The system is segmented into specialized subsystems: measurement subsystem for environmental sensing, classifier for pattern recognition, and controller for filter selection. This segmentation enables the system to achieve high adaptability to both ambient noise and earspeaker fit changes while managing complexity through modular, specialized components rather than a monolithic complex system.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS11948546B2Feed-forward adaptive noise-canceling with dynamic filter selection based on classifying acoustic environment

Publication Date: 2024.04.02 CIRRUS LOGIC INC

AI summary

An adaptive noise-canceling system generates an anti-noise signal from a noise reference signal with a feed-forward filter that filters the noise reference signal to produce the anti-noise signal. The feed-forward filter has a first response controlled by a set of first coefficients. The adaptive noise-canceling system includes a measurement subsystem for measuring a characteristic of an acoustic environment of the adaptive noise-canceling system, a classifier for classifying the characteristic of the acoustic environment by analyzing an output of the measurement subsystem, and a controller that provides the set of first coefficients to the feed-forward filter in conformity with an output of the classifier. The controller may include a look-up table for providing sets of values of the first coefficients to the feed-forward filter in conformity with an indication provided from the classifier and corresponding to a classification of the characteristic of the acoustic environment of the adaptive noise-canceling system.