Null-Forming Microphone Array for Echo Attenuation
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Solution Overview
Problem
In voice communications, the near-to-far ratio decreases due to sound from a loudspeaker reaching microphones simultaneously with sound from a near end talker, leading to poor acoustic performance, as the microphones struggle to distinguish between the two signals during double talk scenarios.
Innovation Solution
The implementation of null-forming techniques using a microphone array to form directional acoustic nulls and beams, where acoustic nulls are oriented towards the loudspeaker and acoustic beams are oriented towards the near end talker, enhancing the near-to-far ratio by attenuating echo and amplifying the near end talker's sound.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the microphones capture sound from both the near end talker and the loudspeaker simultaneously, then the microphones can record all present sounds, but the near-to-far ratio decreases and acoustic performance deteriorates
Solution Approach 1:
The patent applies local quality by creating directional sensitivity patterns for different microphone elements. Each microphone in the array is assigned specific weights that emphasize sounds from certain directions (near end talker) while de-emphasizing sounds from other directions (loudspeaker). This directional weighting allows the system to capture all sounds while selectively prioritizing the near end talker's voice, thereby improving the near-to-far ratio without sacrificing overall sound capture completeness.
2Measurement precision
If acoustic echo cancellation is used to reduce echo, then the acoustic performance improves, but the system complexity increases
Solution Approach 1:
The patent segments the acoustic signal processing into distinct functional components: directional beamforming to isolate the near end talker, echo path modeling to characterize the acoustic environment, and adaptive filtering to cancel echo. By dividing the complex echo cancellation task into these manageable segments, the system achieves improved acoustic performance while keeping each component's complexity controlled and manageable.
Solution Approach 2:
The patent introduces an intermediary echo path model that mediates between the loudspeaker signal and the microphone signals. This model serves as a bridge to estimate and subtract the echo component from the microphone recordings. By using this intermediary representation, the system can effectively cancel echo without requiring direct complex interactions between all system components, thereby managing system complexity.
3Adaptability or versatility
If the near end talker is positioned far from the microphones, then the device design is flexible, but the near end signal strength decreases relative to the echo
Solution Approach 1:
The patent transitions from considering only the spatial distance between the near end talker and microphones to utilizing the angular/directional dimension. By implementing a microphone array with directional beamforming capabilities, the system can distinguish between sounds based on their direction of arrival rather than just proximity. This allows the near end talker to be positioned at various distances while maintaining a high near-to-far ratio through directional selectivity, thereby preserving device design flexibility.
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
This approach significantly improves the near-to-far ratio and overall acoustic performance by effectively reducing echo and enhancing the quality of sound received by the far end talker, allowing for clearer communication.
Implementation Method 1
form directional acoustic nulls and directional acoustic beams using a microphone array. The acoustic nulls may be oriented in the direction from which the loudspeaker signal is arriving. Forming an acoustic null may comprise attenuating sound captured by the microphones from the direction of the acoustic nulls.
Implementation Method 2
at least one of the acoustic beams may be oriented in the direction of a near end talker of the communication device. Forming an acoustic beam may comprise amplifying sound captured by the microphones from the direction of the acoustic beam.
Data Source
AI summary
A plurality of microphones of a communication device is grouped into multiple microphone groups, such that each microphone group includes two or more microphones. For each microphone group, output of the corresponding microphones is processed to form an acoustic null in a corresponding spatial direction, such that sound from the corresponding spatial direction is attenuated in the processed output. One of the microphone groups is selected based on various factors leading to maximal echo attenuation and rejection of reverberant components of the room. The selected microphone group is then used to detect sound from a near end talker of the communication device.