Laser Vibrometry Sound Localization Behind Solid Structures
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Solution Overview
Problem
Existing sound source localization technologies are limited to open spaces where the line of sight between sensors and the sound source is unblocked, preventing effective localization behind or inside solid structures.
Innovation Solution
A system utilizing at least four emitter/receiver pairs with laser emitters and receivers positioned externally to a structure, directing laser beams onto reflector surfaces to measure vibration signals, converting them to acoustic signals, and processing these signals to determine the sound source location within the enclosed structure using time difference of arrival (TDOA) analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional sound source localization methods (beamforming, triangulation) are used with microphones in open spaces, then accurate localization can be achieved when line of sight is unblocked, but the method fails when the sound source is behind or inside solid structures blocking the line of sight
Solution Approach 1:
The patent introduces an intermediary approach by using the solid structure itself as a transducer. Sound waves from the source cause vibrations in the structure, which then radiate sound externally. This converts the blocking structure into a useful intermediary that carries acoustic information from the hidden source to external sensors, resolving the line-of-sight limitation.
Solution Approach 2:
The patent replaces the traditional acoustic transmission path (sound waves traveling directly through air) with a mechanical transmission path (sound-induced vibrations in the solid structure). This substitution allows localization of sources that are acoustically blocked, as the mechanical vibrations in the structure preserve the acoustic information.
2Measurement precision
If microphones are placed inside or near the structure to detect sound, then direct acoustic measurement is possible, but the system becomes complex and requires knowledge of the target structure's internal geometry and components
Solution Approach 1:
The patent applies self-service by allowing the external sensors and processing system to extract all necessary information from the structure's external surface vibrations. The system serves itself by using only external measurements, eliminating the need for internal microphone placement or prior knowledge of internal structure geometry.
Solution Approach 2:
The patent changes the 'state' of the structure from being an acoustic barrier to being an acoustic signal carrier. By detecting vibrations on the external surface, the system effectively 'sees through' the structure, analogous to changing the optical properties of an object to make it transparent or translucent to detection.
3Loss of information
If trial-and-error approaches are used to determine sound source location behind partitions, then some localization information can be obtained, but vast knowledge of the target structure and its components is required to achieve accurate locations
Solution Approach 1:
The patent creates a universal system that can localize sound sources behind any type of structure regardless of material, geometry, or internal configuration. The method works by detecting external vibrations caused by sound-induced structural response, making it adaptable to diverse structures without requiring structure-specific knowledge or calibration.
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 accurate localization of sound sources within solid enclosures by measuring vibration-induced reflections on the structure's surface, effectively 'seeing' through the enclosure to determine the source's location, applicable in rescue operations, noise analysis, and military intelligence.
Implementation Method 1
measuring vibration signals from at least four reflector surfaces on an outer surface of the enclosed structure
Implementation Method 2
measuring vibration signals from at least four reflector surfaces on an outer surface of the enclosed structure with at least four lasers
Implementation Method 3
The receiver receives vibrational signals from the laser beam on the surface at the respective reflector surface location and converting the vibrational signals to acoustic signals
Implementation Method 4
The laser directs a laser beam onto a respective reflector surface location on an outer surface of the structure, the respective reflector surface location being caused to vibrate due to sound waves generated from a sound source
Data Source
AI summary
A system for locating a sound source includes at least four emitter/receiver pairs, each emitter/receiver pair of the at least four emitter/receiver pairs including a laser emitter and a receiver external to an enclosed structure. The laser directs a laser beam onto a respective reflector surface location on an outer surface of the structure, the respective reflector surface location being caused to vibrate due to sound waves generated from a sound source at a sound source location within the enclosed structure. The receiver receives vibrational signals from the laser beam on the surface at the respective reflector surface location and converting the vibrational signals to acoustic signals. A processor coupled to the emitter/receiver pairs for utilizing the acoustic signals to determine a time difference of arrival of the sound waves to the respective reflector surface locations to determine the sound source location based on the time difference of arrivals.