Direction of Arrival Estimation Using Reference Signal Extraction
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Solution Overview
Problem
Existing direction of arrival techniques for sound detection in head-wearable devices fail to accurately and continuously estimate the location of a target sound source in noisy environments with multiple sound sources, often reflecting the direction of dominant sounds instead, leading to ambiguities.
Innovation Solution
A method that calculates interaural time and level differences using a beamformer technique, Fourier transforms, and power difference measures across multiple frequency channels, comparing high and low frequency sound estimates to improve direction of arrival accuracy, and optionally using bilateral beamformers or radio links to steer the sound detection beam and reintroduce localization cues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cross-correlation between microphone output signals is used to determine delay, then direction of arrival can be estimated in quiet environments, but the system fails to accurately estimate direction in noisy environments with multiple sound sources
Solution Approach 1:
The patent extracts the target sound signal from the noisy mixture by using a reference signal that represents only the target sound. This reference signal is obtained through a separate microphone positioned near the target sound source, allowing the system to isolate and process only the relevant signal components while filtering out interfering sounds from other sources.
Solution Approach 2:
The patent introduces a reference signal as an intermediary element that mediates between the noisy microphone outputs and the direction estimation process. This reference signal serves as a clean template against which the microphone signals are compared, enabling accurate time delay measurement even in the presence of multiple sound sources and background noise.
2Reliability
If bilateral beamforming is used to improve Signal-to-Noise ratio, then noise reduction is achieved, but localization cues are removed
Solution Approach 1:
The patent segments the signal processing into distinct stages: first applying bilateral beamforming to improve Signal-to-Noise ratio, then separately calculating interaural time differences and interaural level differences to preserve localization cues. This segmentation allows each processing stage to optimize for its specific function without compromising the other.
Solution Approach 2:
The patent performs preliminary beamforming processing to enhance the Signal-to-Noise ratio before proceeding with direction estimation calculations. By improving the signal quality in advance, the subsequent localization calculations can operate on cleaner data, maintaining accuracy while benefiting from noise reduction.
3Productivity
If dominant sound tracking is used, then direction estimation responds to strongest sounds, but temporal fluctuations create ambiguities in target sound localization
Solution Approach 1:
The patent uses the reference signal as a feedback template to continuously guide the direction estimation process. By comparing the microphone outputs against this stable reference, the system maintains consistent tracking of the target sound source regardless of temporal fluctuations in dominant sound sources, eliminating ambiguities in localization.
Data Source
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AI summary
Systems and methods for estimating the direction of arrival of sounds are disclosed, one method including the steps of: forming a reference signal; detecting sound with two or more spatially separated, directional or spatially separated directional, microphones to produce two or more output signals; calculating the relationships between each of the two or more output signals and the reference signal; and estimating the direction of arrival based on differences between the relationships.