Echo Cancellation Using Sensitivity Patterns for Delay Estimation
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Solution Overview
Problem
Existing echo cancellation systems in teleconferencing fail to accurately measure delay times due to microphone characteristics, leading to ineffective echo suppression, especially with directional microphones where direct waves are masked by reflected waves.
Innovation Solution
An echo cancellation apparatus with a generating unit for sensitivity signals, a delay estimating unit to determine the shortest delay time, and an echo suppressing unit that uses these estimates to suppress echoes, regardless of microphone characteristics, by employing multiple microphone elements and sensitivity patterns to differentiate between direct and reflected waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a directional microphone with high sensitivity on the talker side is used to prevent echoes from entering the microphone, then echo prevention is improved, but the sensitivity on the speaker side becomes low, making it difficult to sense the direct wave
Solution Approach 1:
The patent divides the delay time measurement process into multiple segments by generating multiple sensitivity signals with different sensitivity patterns. Each sensitivity signal processes the microphone signals with a specific directional pattern, allowing the system to segment the measurement task across multiple processing channels to find the direct wave delay time despite the directional microphone's limited speaker-side sensitivity
Solution Approach 2:
The patent changes the sensitivity pattern parameter by generating multiple sensitivity signals with different sensitivity patterns. This parameter change allows the system to adaptively search for the direct wave across different directional characteristics, enabling accurate delay time measurement even when the physical microphone has low sensitivity on the speaker side
2Productivity
If delay time estimation is performed using reflected waves mistaken as direct waves, then delay time estimation can be completed, but accurate delay time measurement fails
Solution Approach 1:
The patent employs feedback by using the correlation results from multiple sensitivity signals to iteratively identify the correct direct wave delay time. The system compares delay times obtained from different sensitivity patterns and uses this feedback to distinguish the true direct wave from reflected waves, ensuring accurate delay time measurement
Solution Approach 2:
The patent creates multiple sensitivity signals that can serve different directional patterns, making the system universal in handling different wave arrival scenarios. This multi-functionality allows the same processing framework to identify direct waves regardless of which sensitivity pattern captures them most effectively
Data Source
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AI summary
An echo cancellation apparatus is connectable to a speaker configured to output speaker signals and a microphone configured to receive a sound from the speaker and including a plurality of microphone elements. The echo cancellation apparatus includes: a generating unit configured to generate a plurality of sensitivity signals having different sensitivity patterns which represent directionality of the microphone, based on a plurality of microphone signals obtained from the respective microphone signals; a delay estimating unit configured to determine a shortest delay time as an estimated delay time, the shortest delay time being a shortest one of delay times between the speaker signals and the microphone signals, the delay times being obtained from the respective sensitivity signals; and an echo suppressing unit configured to suppress echoes of the plurality of microphone signals using the estimated delay time.