Microphone Signal Attenuation Using Cross-Correlation for Echo Control
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Solution Overview
Problem
Conventional methods for mitigating acoustic echo and audio feedback are ineffective when separate audio capture and output devices are used, as they fail to account for unpredictable delays and signal processing variations, leading to echo and feedback issues in communications sessions.
Innovation Solution
A method involving correlating audio signals from separate loudspeakers with microphone signals to determine a time delay and alignment, followed by attenuation based on signal similarity, to reduce echo and feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional echo mitigation methods are used with separate audio capture and output devices, then device simplicity is maintained, but echo and feedback suppression effectiveness deteriorates due to unpredictable delays and signal processing variations
Solution Approach 1:
The patent replaces conventional mechanical/acoustic echo cancellation methods with a signal processing approach that uses cross-correlation analysis. Instead of relying on fixed delay compensation, the system dynamically determines time delays by correlating microphone signals with loudspeaker output signals, allowing adaptive echo suppression that accounts for unpredictable variations in separate devices.
Solution Approach 2:
The system dynamically adjusts the attenuation parameter based on the correlation between microphone signals and loudspeaker signals. By calculating cross-correlation values and determining time delays, the system adaptively changes the attenuation applied to microphone signals, optimizing echo suppression for varying conditions between separate audio devices.
2Object-affected harmful factors
If microphone signals are attenuated to reduce echo, then echo and feedback are suppressed, but audio signal quality and volume deteriorate
Solution Approach 1:
The patent applies attenuation locally and selectively to specific portions of the microphone signal that contain echo content. By using cross-correlation to identify the timing and characteristics of echoed signals, the system applies attenuation only to the correlated echo portions while preserving the original speech signal quality, rather than uniformly attenuating the entire microphone signal.
Solution Approach 2:
The system creates a copy of the loudspeaker signal through cross-correlation with the microphone signal to identify echo components. This copied reference signal is then used to selectively attenuate only the echo portions detected in the microphone signal, preserving the quality of non-echo portions of the audio.
3Measurement precision
If cross-correlation analysis is performed to determine time delay and alignment, then echo suppression accuracy is improved, but computational complexity increases
Solution Approach 1:
The patent performs cross-correlation analysis selectively rather than continuously on the entire audio spectrum. By focusing correlation calculations on relevant frequency ranges and time windows where echo is most likely to occur, the system achieves accurate time delay determination while reducing unnecessary computational complexity from analyzing all audio data at all times.
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
Effectively attenuates microphone signals to minimize acoustic echo and audio feedback by aligning and adjusting signal levels based on correlation analysis, improving audio quality in communications systems.
Implementation Method 1
means for correlating a first combination of the first and second audio signals with the one or more microphone signals; means for determining a time delay at which the first combination of the first and second audio signals is most similar to the one or more microphone signals
Data Source
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AI summary
Various example embodiments relate to microphone signal attenuation. An example method may comprise receiving one or more microphone signals from respective microphones for capturing first and second audio signals output by respective first and second loudspeakers and correlating a first combination of the first and second audio signals with the one or more microphone signals. The method may also comprise determining a time delay at which the first combination of the first and second audio signals is most similar to the one or more microphone signals. The method may also comprise aligning, or causing alignment of, the first and second audio signals to the one or more microphone signals based on the time delay, and attenuating, or causing attenuation of, the one or more microphone signals by an attenuation amount determined based at least in part on a second combination of the aligned first and second audio signals.