Adaptive Noise-Canceling Circuit Ambient Noise Training

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Solution Overview

Problem

Existing personal audio devices with adaptive noise cancellation (ANC) systems face challenges in updating the secondary path estimate when source audio is absent, leading to inaccurate noise cancellation, especially at the beginning of a telephone conversation.

Innovation Solution

The implementation of an adaptive noise-canceling circuit that uses ambient noise as a training signal to adapt the secondary path estimate, independent of the presence of source audio, by employing a secondary path adaptive filter and a primary path modeling adaptive filter to minimize error signals and maintain effective noise cancellation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the secondary path estimate is updated using source audio, then the noise cancellation accuracy is improved, but the system cannot adapt when source audio is absent

Engineering Contradiction:

Improvenoise cancellation accuracyVSAvoidadaptation capability

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent introduces ambient noise as an intermediary training signal to update the secondary path estimate when source audio is absent. The adaptive noise-canceling circuit processes ambient noise through the secondary path adaptive filter to generate an update signal, which serves as a substitute for source audio-based updates, enabling continuous adaptation of the secondary path model regardless of source audio availability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system dynamically changes the training signal parameter based on the presence of source audio. When source audio is detected, it is used for updating the secondary path estimate; when source audio is absent, the system switches to using ambient noise as the training signal. This parameter switching enables the system to maintain adaptation capability across different operating conditions

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If the secondary path estimate is not updated when source audio is absent, then the system remains simple to operate, but noise cancellation accuracy deteriorates over time

Engineering Contradiction:

Improvesystem operation simplicityVSAvoidnoise cancellation accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The system performs self-updating of the secondary path estimate using ambient noise as a freely available resource. The adaptive noise-canceling circuit automatically processes ambient noise through the secondary path adaptive filter and updates the secondary path model without requiring external intervention or complex user operations, maintaining both simplicity and continuous accuracy improvement

Inventive Principle:

Principle #25Self-service

3Adaptability or versatility

If ambient noise is used as a training signal, then the secondary path estimate can be adapted independently of source audio presence, but the system complexity increases

Engineering Contradiction:

Improveadaptation independenceVSAvoidprocessing circuit complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The adaptive noise-canceling circuit performs multiple functions: it processes both source audio and ambient noise, generates anti-noise signals, and updates the secondary path estimate using either training signal source. This multi-functionality is achieved within a unified adaptive filtering framework that handles different input types through the same secondary path adaptive filter structure, minimizing additional complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9208771B2Ambient noise-based adaptation of secondary path adaptive response in noise-canceling personal audio devices

Publication Date: 2015.12.08 CIRRUS LOGIC INC

AI summary

An adaptive noise canceller adapts a secondary path modeling response using ambient noise, rather than using another noise source or source audio as a training source. Anti-noise generated from a reference microphone signal using a first adaptive filter is used as the training signal for training the secondary path response. Ambient noise at the error microphone is removed from an error microphone signal, so that only anti-noise remains. A primary path modeling adaptive filter is used to modify the reference microphone signal to generate a source of ambient noise that is correlated with the ambient noise present at the error microphone, which is then subtracted from the error microphone signal to generate the error signal. The primary path modeling adaptive filter is previously adapted by minimizing components of the error microphone signal appearing in an output of the primary path adaptive filter while the anti-noise signal is muted.