Hybrid Active Noise Reduction Filter Segmentation

Solution Overview

Problem

Active noise reduction systems, both feedback and feedforward types, face challenges in achieving improved performance due to the reliance on the quality of ANC filters, which can be limited by the complexity and power consumption of filter designs, especially in mobile devices.

Innovation Solution

A hybrid noise reduction system is introduced, combining a feedback and feedforward loop with shelving or equalizing filters, allowing for separate optimization of open and closed loop filters, and incorporating analog and digital filters to enhance noise reduction efficiency while minimizing power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If complex ANC filters are used to improve noise reduction performance, then noise reduction quality is improved, but power consumption increases and device complexity increases

Engineering Contradiction:

Improvenoise reduction qualityVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent divides the ANC filter into two separate filters: a first ANC filter for the feedback loop and a second ANC filter for the feedforward loop. This segmentation allows each filter to be independently optimized for its specific function, reducing the overall complexity and power consumption while maintaining noise reduction quality. The feedback filter handles low-frequency noise cancellation, while the feedforward filter handles high-frequency noise, enabling specialized optimization for each frequency range.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs adaptive filtering algorithms that dynamically adjust filter coefficients based on real-time noise characteristics. This dynamic adaptation allows the system to maintain optimal noise reduction performance across varying noise conditions without requiring permanently complex filter structures, thereby reducing average power consumption while preserving reliability.

Inventive Principle:

Principle #15Dynamics

2Reliability

If complex ANC filters are used to improve noise reduction performance, then noise reduction quality is improved, but device complexity increases

Engineering Contradiction:

Improvenoise reduction qualityVSAvoidfilter design complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent divides the ANC filter into two separate filters: a first ANC filter for the feedback loop and a second ANC filter for the feedforward loop. This segmentation allows each filter to be independently optimized for its specific function, reducing the overall complexity and power consumption while maintaining noise reduction quality. The feedback filter handles low-frequency noise cancellation, while the feedforward filter handles high-frequency noise, enabling specialized optimization for each frequency range.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies different filter characteristics and optimization strategies to different parts of the system: the feedback filter is optimized for low-frequency noise with specific pole-zero configurations, while the feedforward filter is optimized for high-frequency noise with different structural parameters. This local quality approach allows each filter to have tailored complexity appropriate to its function, reducing overall device complexity while maintaining high noise reduction quality.

Inventive Principle:

Principle #3Local quality

3Reliability

If feedback ANC system is used, then noise reduction is achieved, but performance is limited by filter quality

Engineering Contradiction:

Improvenoise reduction capabilityVSAvoidfilter quality dependency

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges feedback ANC and feedforward ANC into a hybrid system that combines the advantages of both approaches. The feedback loop provides accurate low-frequency noise cancellation through error signal processing, while the feedforward loop provides high-frequency noise reduction through reference signal processing. This combination reduces dependency on any single filter's quality while achieving broader frequency range noise reduction.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent introduces a summing junction as an intermediary that combines the output signals from both the feedback and feedforward paths. This intermediary structure allows the system to leverage the strengths of both ANC approaches simultaneously, reducing the performance limitations inherent in using either feedback or feedforward systems alone, without requiring excessively complex individual filters.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS10325586B2Active noise reduction

Publication Date: 2019.06.18 HARMAN BECKER AUTOMOTIVE SYST GMBH

AI summary

A noise reducing comprises a first microphone that picks up noise signal at a first location and that is electrically coupled to a first microphone output path; a loudspeaker that is electrically coupled to a loudspeaker input path and that radiates noise reducing sound at a second location; a second microphone that picks up residual noise from the noise and the noise reducing sound at a third location and that is electrically coupled to a second microphone output path; a first active noise reducing filter that is connected between the first microphone output path and the loudspeaker input path; and a second active noise reducing filter that is connected between the second microphone output path and the loudspeaker input path; in which the first active noise reduction filter is a shelving or equalization filter or comprises at least one shelving or equalization filter or both.