Dynamic Range Compression for Nonlinear Echo Mitigation

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Solution Overview

Problem

Conventional acoustic echo cancellers struggle with nonlinear echoes from low-quality loudspeakers and vibrating devices, leading to distortion and poor audio quality, as they assume a linear system that often does not accurately model the loudspeaker's acoustic response.

Innovation Solution

Dynamic range compression is applied to the audio signal before output, using a compression curve and attenuation factor to reduce nonlinear echo components by lowering peak amplitudes while maintaining loudness, thereby improving audio quality and reducing distortion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a linear adaptive filter is used to model the acoustic room impulse response, then linear echo components can be attenuated, but nonlinear echo components from poor loudspeaker quality and vibrating parts cannot be reduced

Engineering Contradiction:

Improveecho cancellation effectivenessVSAvoidmodeling accuracy for nonlinear systems

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent applies dynamic range compression to modify the audio signal parameters before they reach the loudspeaker. By compressing the dynamic range and reducing peak amplitudes, the signal is transformed to operate within a linear region of the loudspeaker's transfer function, thereby preventing nonlinear distortion from occurring in the first place

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The dynamic range compression is applied in advance to the audio signal before it is sent to the loudspeaker. This preliminary processing ensures that the signal peaks are reduced beforehand, preventing the loudspeaker from operating in its nonlinear region and eliminating the need for complex nonlinear echo cancellation

Inventive Principle:

Principle #10Preliminary action

2Power

If the loudspeaker operates at high volume settings, then audio output quality may be improved, but nonlinear distortion and rattling from vibrating parts increase

Engineering Contradiction:

Improveaudio output powerVSAvoidnonlinear distortion and vibration

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The dynamic range compression algorithm changes the amplitude parameters of the audio signal by applying a compression curve. This reduces peak amplitudes while maintaining the perceived loudness through make-up gain, allowing the system to operate at lower power levels that avoid nonlinear distortion and mechanical vibration

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the potential harm of high power operation (which causes nonlinear distortion) into a benefit by using dynamic range compression to achieve perceived loudness through controlled peaks rather than sustained high power, thereby eliminating distortion while maintaining audio quality

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Device complexity

If a conventional acoustic echo canceller is used, then the system complexity remains low, but nonlinear echo components deteriorate audio signal quality

Engineering Contradiction:

Improveecho canceller structureVSAvoidaudio signal quality

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The dynamic range compression acts as an intermediary processing stage between the audio source and the loudspeaker. By preprocessing the signal to remove peaks that cause nonlinear distortion, it protects the subsequent echo cancellation system from having to deal with nonlinear components, maintaining simplicity while improving quality

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS8660676B2Mitigating the impact of nonlinear echos by dynamic range compression

Publication Date: 2014.02.25 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

Mitigation of nonlinear echoes by dynamic range compression may be provided. An audio output may be evaluated to determine whether nonlinear echoes are interfering with an audio signal. In order to reduce such nonlinear echoes, a dynamic range compression algorithm may be applied to the audio signal prior to output. The signal may be modified according to a compression wave and/or subjected to an attenuation factor.