Subband Active Noise Cancellation With Low-Delay DSP Filtering

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Solution Overview

Problem

Analog active noise cancellation (ANC) systems face challenges such as acoustic feedback, limited noise cancellation for periodic or quasi-stationary signals, and frequency range limitations, while digital ANC systems suffer from latency and power consumption issues, making them impractical for portable applications.

Innovation Solution

The implementation of an over-sampled subband adaptive filtering system using specialized DSP methods and apparatuses, which includes a first and second over-sampled analysis filterbank, a subband processing module, and an over-sampled synthesis filterbank to process and adjust subband adaptive filters, reducing processing delay and improving noise cancellation across a broader frequency range.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If digital signal processing (DSP) is used to perform ANC, then noise cancellation performance is improved, but processing delay increases

Engineering Contradiction:

Improvenoise cancellation performanceVSAvoidprocessing delay

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent divides the frequency spectrum into multiple subbands using filter banks, allowing parallel processing of different frequency components. This segmentation enables the system to achieve effective noise cancellation across a broad frequency range while maintaining low processing delay, as each subband can be processed independently and efficiently

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs periodic sampling and block-based processing in the subband domain, transforming continuous signal processing into discrete periodic operations. This approach reduces computational complexity and processing delay while maintaining effective noise cancellation performance through systematic processing of signal blocks

Inventive Principle:

Principle #19Periodic action

2Measurement precision

If fully digital ANC systems are implemented, then noise cancellation capability is improved, but power consumption increases

Engineering Contradiction:

Improvenoise cancellation capabilityVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

By segmenting the signal into subbands and processing them in parallel, the system achieves effective noise cancellation with reduced computational complexity per processing unit. This allows implementation on low-power hardware platforms while maintaining broad frequency range cancellation capability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent replaces complex full-band digital signal processing with a more efficient subband processing architecture that uses simpler computational operations in each subband. This substitution reduces the overall computational burden and power consumption while achieving comparable or superior noise cancellation performance

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If DSP-based ANC systems are used, then noise cancellation performance is improved, but device size increases

Engineering Contradiction:

Improvenoise cancellation performanceVSAvoiddevice size

Core Design Contradiction:

Measurement precisionVSVolume of moving object

Solution Approach 1:

The subband processing architecture segments the computational workload across multiple simple processing units rather than requiring a single complex DSP processor. This segmentation enables implementation in compact form factors suitable for portable hearing devices while maintaining effective noise cancellation performance

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transforms the signal processing approach by changing from time-domain full-band processing to frequency-domain subband processing. This parameter change in the processing domain enables more efficient hardware implementation with reduced device size while achieving broad frequency range noise cancellation

Inventive Principle:

Principle #35Parameter changes

4Device complexity

If analog ANC systems are used, then device complexity is reduced, but noise cancellation effectiveness decreases

Engineering Contradiction:

Improvesystem complexityVSAvoidnoise cancellation effectiveness

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent combines simple analog subband filtering with efficient digital processing in each subband, achieving effective noise cancellation with reduced overall system complexity. The analog filter banks provide straightforward frequency separation while digital processing in each subband handles the adaptive cancellation with minimal computational requirements

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent replaces complex full-band digital signal processing with a hybrid approach using analog filter banks for frequency separation and simple digital processing in each subband. This substitution achieves effective noise cancellation with reduced computational complexity and simpler system architecture

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS8280065B2Method and system for active noise cancellation

Publication Date: 2012.10.02 GN HEARING AS

AI summary

A method and system for active noise cancellation is provided. The system employs subband processing, and preferably implements over-sampled filterbank. The system is applicable to adaptive noise cancellation, adaptive echo cancellation for portable listening devices, such as headsets and other similar listening devices.