Spectrum Envelope Echo Suppression for Loudspeaker Nonlinear Distortion

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Solution Overview

Problem

Conventional echo suppression techniques struggle to stably suppress nonlinear echo signals, particularly in systems with loudspeaker distortion, leading to reduced call quality.

Innovation Solution

An echo suppressing device that includes a first linear echo suppression unit to estimate and suppress linear echo signals, a spectrum envelope extraction unit to extract relevant information, a nonlinear echo estimation unit to estimate the spectrum envelope of nonlinear echo signals, and a nonlinear echo suppression unit to suppress these signals using the estimated envelope information.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional echo suppression techniques are used, then linear echo signals can be suppressed, but nonlinear echo signals cannot be stably suppressed

Engineering Contradiction:

Improveecho suppression stabilityVSAvoidnonlinear echo signal handling

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The echo suppression process is divided into two independent segments: linear echo suppression (using conventional techniques on the reception signal) and nonlinear echo suppression (using spectrum envelope estimation on the residual signal). This segmentation allows each segment to be optimized for its specific type of echo, resolving the contradiction between reliable linear suppression and adaptability to nonlinear echoes.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the parameter representation from raw time-domain signals to spectrum envelope information. By estimating spectrum envelope characteristics (amplitude and phase) of nonlinear echo signals and applying frequency-domain filtering, the system gains adaptability to handle nonlinear distortions while maintaining stable suppression performance.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If spectrum envelope information is extracted from multiple signals, then estimation accuracy improves, but processing complexity increases

Engineering Contradiction:

Improvenonlinear echo estimation accuracyVSAvoidsignal processing complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The system performs preliminary linear echo suppression before nonlinear echo estimation. By removing the linear echo component first, the subsequent nonlinear echo estimation operates on a cleaner signal, improving accuracy without requiring complex simultaneous processing of all echo types.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention introduces spectrum envelope information as an intermediary representation between the time-domain signals and the final echo suppression output. This intermediary form simplifies the estimation process by focusing on essential spectral characteristics rather than processing complete signal waveforms, reducing complexity while maintaining precision.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12490024B2Echo suppressing device, echo suppressing method, and non-transitory computer readable recording medium storing echo suppressing program

Publication Date: 2025.12.02 PANASONIC INTELLECTUAL PROPERTY CORP OF AMERICA

AI summary

An echo suppressing device includes: an echo canceller that suppresses a linear echo signal from an input signal acquired by a microphone; a spectrum envelope extraction unit that extracts spectrum envelope information from a reception signal to be output to a loudspeaker; a nonlinear echo estimation unit that estimates spectrum envelope information of a nonlinear echo signal included in the input signal from the spectrum envelope information extracted from the reception signal; and a nonlinear echo suppression unit that suppresses the nonlinear echo signal from an output signal of the echo canceller by using the estimated spectrum envelope information of the nonlinear echo signal.