Directional Microphone Echo Geometry Detection
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Solution Overview
Problem
Conventional directional microphone units placed near hard surfaces experience interference from reflected echoes, which can disrupt speech recognition and other audio processing tasks, as existing echo cancellation techniques only address echoes from known sources and not external sound reflections.
Innovation Solution
The method involves using the directional microphone unit to detect the geometry of the system by analyzing the constructive and destructive interference patterns of white noise echoes and direct signals, allowing the system to calculate the source direction and adjust the receive beam or sensors accordingly to target or avoid the noise source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the directional microphone unit is placed near a hard surface, then the device can be positioned in common locations (e.g., smart TV near wall), but the reflected echo interferes with directly received sound, causing speech recognition failures
Solution Approach 1:
The patent converts the harmful echo reflection into a useful signal source. By analyzing the interference pattern between direct sound and reflected echo, the system determines the direction of the sound source. The echo, which was previously causing interference and recognition failures, is now exploited to calculate geometric relationships and improve directional accuracy, especially when combined with beam-forming techniques to enhance signals from the determined direction.
2Object-generated harmful factors
If conventional AEC techniques are used to remove echoes, then echoes from known internal sources can be cancelled, but external sound source echoes cannot be removed as the device does not issue these sounds
Solution Approach 1:
Instead of trying to cancel external echoes by generating opposite signals (which requires knowing the external sound source, which is impossible), the patent inverts the approach by using the interference pattern created by external echoes to determine sound source direction. Rather than attempting to remove the harmful effect through active cancellation, the system passively analyzes the interference pattern to extract directional information, making the system adaptable to external sound sources without requiring them to be known or controllable.
3Measurement precision
If the receive beam is directed toward the sound source, then speech recognition accuracy improves, but the system cannot determine the source direction when echoes interfere with the direct signal
Solution Approach 1:
The patent uses feedback from the interference pattern itself to improve direction detection. By analyzing the frequency response characteristics created by the interaction between direct sound and reflected echo, the system extracts directional information about the sound source. This feedback loop allows the system to determine the optimal beam direction even in the presence of echo interference, and then use beam-forming to enhance signals from that direction while suppressing interference from other directions.
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 enhances speech recognition by directing the receive beam towards the intended source, improving signal quality and reducing interference from unwanted noise sources, such as external appliances or reflections from multiple surfaces.
Implementation Method 1
the hard surface reflects back an echo which may interfere with the directly received instance of the same sound
Implementation Method 2
the system formed by the source, microphone unit and reflecting surface will have a certain frequency response whereby at some frequencies the echo will constructively interfere with the direct path and at other frequencies the echo will destructively interfere
Data Source
AI summary
A method of using a directional microphone unit having an array of constituent microphones. Each of a plurality of the microphones receives substantially white noise via a direct path from a source, and also receives an echo comprising a reflection of the white noise from at least one surface, thereby obtaining a received noise signal comprising a combination of the directly-received noise and the echo. For each of the plurality of microphones, a spacing is identified between lobes and/or troughs in a respective spectrum of the received noise signal as received by the respective microphone, thereby determining an additional distance travelled by the echo to the respective microphone relative to the direct path. A direction of the source is calculated based on the additional distance travelled for each of said plurality of microphones.