Pseudo-Ambisonics Signal Generation for Wearable Sound Localization
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Solution Overview
Problem
Existing wearable microphones face challenges in accurately determining sound source direction due to non-uniform microphone placement on a spherical surface, making it difficult to convert collected acoustic signals into ambisonics signals for sound event localization and detection (SELD).
Innovation Solution
A pseudo-ambisonics signal generating apparatus that uses a spherical coordinate system with an origin at the intersection of the line between the ears and a face-dividing plane, calculates an average radius, and generates pseudo-ambisonics signals from acoustic data, enabling estimation of sound source direction and type.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If microphones are disposed on a spherical surface for ambisonics signal calculation, then measurement precision of three-dimensional sound field is improved, but ease of operation deteriorates due to difficulty in disposing microphones on same spherical surface when mounted on human head
Solution Approach 1:
The patent changes the coordinate system parameters from strict spherical coordinates requiring equal radius to pseudo-spherical coordinates with varying radii. Each microphone is assigned individual spherical coordinates (rq, φq, θq) where the radius rq can differ for each microphone position on the head, allowing flexible placement while maintaining the mathematical framework for ambisonics signal calculation
Solution Approach 2:
The patent segments the spherical coordinate system into individual microphone-specific coordinates rather than requiring a unified spherical surface. Each of the Q microphones is assigned its own set of spherical coordinates independently, allowing them to be positioned at different distances from the origin while still enabling ambisonics signal generation
2Measurement precision
If higher-order spherical harmonics are used for expansion, then measurement precision of three-dimensional sound field is improved, but device complexity increases due to requiring more microphones
Solution Approach 1:
The patent applies partial action by using only the necessary components of spherical harmonics expansion (up to first order with l ≤ 2) rather than requiring complete higher-order expansion. This allows obtaining sufficient measurement precision for sound source direction estimation without implementing the full complexity of high-order ambisonics that would require many more microphones
Data Source
AI summary
Make it possible to obtain a pseudo acoustic intensity vector using an acoustic signal collected by a wearable device. To this end, a pseudo-ambisonics signal generating apparatus according to the disclosed technology includes a spherical coordinate acquisition unit, a calculation unit, and a signal extraction unit. The spherical coordinate acquisition unit acquires spherical coordinates of each microphone with an intersection of a plane dividing a face symmetrically to the left and right and a straight line passing through the centers of left and right ears as an origin. The calculation unit calculates an average value of radii of the spherical coordinates, and replaces the radii of the spherical coordinates with the average values. The signal extraction unit generates a pseudo-ambisonics signal using the spherical coordinates replaced with the average values and acoustic signals acquired by the microphones.