Spatial Echo Cancellation via Beamforming for Non-Linear Speaker Interference
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Solution Overview
Problem
Acoustic echo cancellation in audio devices is hindered by non-linear and asynchronous behavior of playback speakers, which can lead to interference in microphone signals, especially when loudspeakers operate beyond their limits or when the reference signal from the playback device is not readily available.
Innovation Solution
The use of spatial information and beamforming techniques to determine echo-dominant audio signals, which are then used as a reference to remove echo from microphone signals, effectively accounting for the asynchronous and non-linear behavior of playback devices by forming pick-up beams that emphasize or de-emphasize specific regions in the listening area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional echo cancelation is used, then echo reduction is achieved, but performance deteriorates when speakers operate non-linearly or asynchronously
Solution Approach 1:
The system dynamically adapts the echo model parameters based on detected non-linear and asynchronous behavior. The echo cancelation system transitions from static parameter settings to dynamic adjustment, where model parameters are modified in real-time according to the playback device's actual acoustic behavior, enabling effective echo reduction under varying operating conditions.
Solution Approach 2:
The system changes the parameters of the echo model to account for non-linear speaker behavior and asynchronous operation. By adjusting model parameters such as delay times, scaling factors, and transfer function characteristics, the echo cancelation algorithm remains accurate even when speakers operate beyond linear ranges or exhibit time-varying behavior.
2Reliability
If playback reference signal is used for echo cancelation, then echo removal is improved, but the system fails when reference signal is not readily available
Solution Approach 1:
The system uses an intermediary approach by estimating the playback reference signal through acoustic measurements when the direct reference is unavailable. Microphones capture the actual acoustic output, and this measured signal serves as an intermediary reference that allows echo cancelation to proceed even when the original digital reference signal cannot be accessed.
Solution Approach 2:
The system implements feedback-based echo estimation by using microphone signals to infer the playback reference. The acoustic feedback loop allows the system to reconstruct the reference signal from the actual acoustic environment, enabling continuous echo cancelation operation regardless of reference signal availability at the source device.
3Measurement precision
If echo cancelation processing is applied, then speech recognition accuracy is improved, but computational complexity increases
Solution Approach 1:
The system applies partial echo cancelation by focusing computational resources on the most significant echo paths and frequency ranges. Rather than processing all possible echo components equally, the system identifies and cancels only the dominant echo contributions, achieving sufficient speech recognition accuracy with reduced computational complexity.
Solution Approach 2:
The echo cancelation system segments the audio processing into distinct stages: echo path identification, model parameter estimation, and adaptive cancellation. This segmentation allows each module to be optimized independently, reducing overall computational complexity while maintaining speech recognition accuracy through specialized processing at each stage.
Data Source
AI summary
A plurality of microphone signals can be captured with a plurality of microphones of the device. One or more echo dominant audio signals can be determined based on a pick-up beam directed towards one or more speakers of a playback device. Sound that is emitted from the one or more speakers and sensed by the plurality of microphones can be removed from plurality of microphone signals, by using the one or more echo dominant audio signals as a reference, resulting in clean audio.