Comfort Noise Injection for Residual Echo Suppression
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Solution Overview
Problem
Communication devices often create abrupt transitions to silence in audio output signals due to residual echo suppression, leading remote listeners to mistakenly believe the communication link is dead, as residual echo suppressors eliminate both echo and background noise.
Innovation Solution
Incorporating a noise generator module that injects comfort noise into the audio signal, matching the spectral characteristics of the original background noise, to maintain an audible noise level and mask residual echoes, ensuring the communication link appears active.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a residual echo suppressor is used to further reduce echo level, then echo suppression is improved, but background noise is also eliminated causing abrupt transitions to silence
Solution Approach 1:
The patent extracts only the noise component from the audio signal for suppression, while preserving the echo component. The residual echo suppressor is modified to selectively reduce background noise levels without completely eliminating them, thereby maintaining continuous audio output and preventing abrupt transitions to silence that would otherwise occur when both echo and noise are suppressed together
Solution Approach 2:
The patent applies different processing qualities to different components of the audio signal. Background noise is suppressed to a controlled level rather than completely eliminated, while echo suppression maintains its effectiveness. This localized differential treatment allows the system to achieve good echo suppression while maintaining a natural listening environment with continuous audio output
2Reliability
If residual echo suppressor eliminates both echo and background noise, then echo level is reduced, but communication link status becomes ambiguous to remote listeners
Solution Approach 1:
The patent converts the potentially harmful effect of complete noise elimination into a benefit by intentionally maintaining a controlled level of background noise. This preserved noise serves as useful information that indicates the communication link is active, transforming what was previously considered unwanted noise into a beneficial status indicator for remote listeners
3Reliability
If residual echo suppressor creates silence during remote user speaking, then echo is suppressed, but listener comfort is reduced due to frequent changes between noise and silence
Solution Approach 1:
The patent ensures continuous audio output by preventing complete elimination of background noise. The residual echo suppressor maintains a continuous noise floor that persists throughout the communication, eliminating the disruptive on/off pattern between noise and silence that occurs when noise is completely removed during speech segments
Data Source
AI summary
Features are disclosed for performing noise compensation so a level of noise may be audible in an output signal. For example, a first noise level of a first signal can be estimated. The first signal can be processed (e.g., by residual echo suppression) to determine a second signal, and a second noise level of the second signal can be estimated. Residual echo suppression can sometimes cause background noise to be eliminated, causing silence. If the second noise level is less than a product of the first noise level and a noise threshold, then a noise signal based on the first noise level can be determined, wherein the noise level of the noise signal is configured to be above a hearing threshold. The noise signal can be combined with the second signal to generate an output signal.