Acoustic Feedback Suppression via Frequency Range Filtering

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Solution Overview

Problem

VoIP users experience acoustic feedback due to the continuous re-capturing and re-rendering of speech signals, leading to energy buildup in specific frequency ranges, which is not effectively mitigated by reducing speaker volume or repositioning microphones and speakers.

Innovation Solution

A system identifies and suppresses the frequency ranges where feedback occurs by disregarding sampling bits or applying filters to attenuate or eliminate the signal, either before rendering or capturing, thereby breaking the feedback loop.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If speaker volume is reduced to avoid feedback, then feedback is suppressed, but audio quality and hearing capability deteriorate

Engineering Contradiction:

ImprovefeedbackVSAvoidhearing capability

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent applies local quality by selectively suppressing only the specific frequency ranges where feedback occurs, rather than uniformly reducing all frequencies. The system identifies feedback frequency ranges and applies suppression locally to those specific bands, preserving audio quality in non-feedback frequency ranges while eliminating feedback in the problematic bands.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If microphones or speakers are repositioned to prevent feedback, then feedback may be reduced, but device portability and ease of operation deteriorate

Engineering Contradiction:

ImprovefeedbackVSAvoiddevice portability

Core Design Contradiction:

Object-affected harmful factorsVSEase of operation

Solution Approach 1:

The patent replaces the mechanical approach of physically repositioning microphones or speakers with a signal processing approach. Instead of mechanically adjusting device positions, the system uses digital signal processing to identify and suppress feedback frequency ranges, thereby eliminating the need for physical repositioning while maintaining device portability and ease of operation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Object-affected harmful factors

If frequency suppression is applied to eliminate feedback, then feedback is reduced, but signal fidelity deteriorates

Engineering Contradiction:

ImprovefeedbackVSAvoidsignal fidelity

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The patent applies dynamics by making the frequency suppression adaptive and dynamic rather than static. The system continuously monitors for feedback and dynamically adjusts which frequency ranges to suppress based on real-time conditions. This allows the suppression to adapt to changing acoustic environments while preserving signal fidelity in frequency ranges that do not exhibit feedback.

Inventive Principle:

Principle #15Dynamics

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

This approach effectively reduces or eliminates feedback without significantly reducing the overall signal volume, allowing for full duplex voice data communications without the need for volume adjustments or physical repositioning of devices.

Implementation Method 1

applying one or more filters to attenuate or eliminate the signal in the frequency range

Methodology Applied

Scientific EffectAcoustic filtering: Filter (physical)

Data Source

PatentUS7764634B2Suppression of acoustic feedback in voice communications

Publication Date: 2010.07.27 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

Suppressing one or more frequency ranges of a signal prevents the occurrence of feedback in a voice data communications application. A system recognizes a frequency range in a signal where feedback occurs, or anticipates a frequency range where feedback is anticipated. The signal includes a signal the input system generates or that the output system renders. The system suppresses the signal in the frequency range by disregarding one or more sampling bits representing the frequency range, or by applying one or more filters to attenuate or eliminate the signal in the frequency range. The system may monitor the signal to identify feedback resulting in different or additional frequency ranges and suppress the signal in the different or additional frequency ranges to prevent feedback from occurring.