Moving Acoustic Source Localization via Specular Reflections
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Solution Overview
Problem
Existing methods struggle to accurately determine the distance between a moving sound source and a microphone when the orientation of reflecting surfaces is unknown, particularly in cases where the sound source moves about, complicating the estimation of acoustic direction of arrival.
Innovation Solution
A method that utilizes specular reflections and geometric properties to estimate the distance and direction of a moving sound source by constructing a system of bi-affine equations based on the generalized velocity vector, incorporating time-frequency transforms and nonlinear minimization to solve for the source's position relative to the microphone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional velocity vector methods are used to determine sound direction and distance, then the method is simple and straightforward, but the accuracy deteriorates when the sound source is moving and reflective surface orientations are unknown
Solution Approach 1:
The patent introduces image sources as intermediary virtual objects that represent reflected sound paths. By calculating positions of these image sources based on known reflective surface orientations, the method creates a mathematical mediator that connects the microphone measurements to the actual moving sound source position, enabling accurate distance determination without directly tracking the moving source
Solution Approach 2:
The patent creates virtual copies (image sources) of the actual sound source by reflecting the source position across known reflective surfaces. These copied virtual sources allow the system to track reflected sound paths independently from the moving actual source, maintaining measurement accuracy while simplifying the mathematical model
2Measurement precision
If the method tracks reflections from known reflective surfaces, then the distance determination accuracy improves, but the complexity increases due to needing to know precise surface orientations
Solution Approach 1:
The patent performs preliminary action by pre-establishing the coordinate systems and orientation relationships for all reflective surfaces before the sound source moves. By defining the reflective surface orientations in advance and calculating initial image source positions, the system prepares the mathematical framework that can then track moving sources without requiring real-time surface measurement
3Adaptability or versatility
If the sound source moves between discrete positions, then the method can capture dynamic sound scenes, but the reliability of distance determination deteriorates when surface orientations are unknown
Solution Approach 1:
The patent implements dynamics by allowing the sound source position to change between discrete time instants while maintaining a fixed coordinate system for the reflective surfaces. The method dynamically recalculates image source positions and distance metrics at each time step based on the new source position, enabling reliable tracking of moving sources through the consistent geometric relationships of the pre-defined reflective surfaces
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
Enables precise estimation of the distance and direction of a moving sound source without prior knowledge of the reflecting surface orientations, leveraging the symmetry of acoustic reflections to refine the determination of distances over time.
Implementation Method 1
exploiting at least one property of the specular reflection, according to which a Euclidean distance between two positions of the source at two discrete points in time is equal to a Euclidean distance between two respective positions of images of the source and derived from one or a plurality of same reflections
Data Source
AI summary
Processing sound signals acquired by at least one microphone, to locate a sound source emitting from a plurality of discrete positions at respective discrete points in time, in a space comprising at least one planar reflective surface. The method includes: obtaining: a first vectoru→0(k)determining a direction of a first acoustic path, direct between the source and the microphone, a second vectoru→n(k)representing a second acoustic path resulting from a specular reflection and arriving at the microphone, and a delayτn(k)of second path at the microphone, compared to the direct path; exploiting a property of the specular reflection according to which a Euclidean distance between two positions of the source at two discrete points in time is equal to a Euclidean distance between two respective positions of images of the source and derived from one or more same reflections, respectively at said two discrete points in time.