Acoustic Survey for Weapons Location in Urban Environments
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Solution Overview
Problem
Urban gunshot location systems face challenges in accurately determining the source of gunfire in complex environments with many buildings, which cause refraction, reflection, and blockage of acoustic waves, leading to errors in location triangulation and sensitivity determination.
Innovation Solution
Conducting an acoustic survey by moving a source through the area to record propagation paths and parameters, including multipath, to improve location determination using pattern recognition and database interpolation, allowing for accurate location correction and sensitivity assessment with fewer sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If acoustic sensors are used to triangulate gunfire locations in urban environments, then location detection capability is improved, but location accuracy deteriorates due to refraction, reflection, and blockage by buildings
Solution Approach 1:
The system performs preliminary acoustic surveys by moving a sound source through the coverage area to record propagation paths and parameters before actual gunfire detection. This preliminary data collection characterizes the acoustic environment including refraction, reflection, and blockage effects, enabling later correction of location accuracy without requiring additional sensors during operational detection
Solution Approach 2:
The patent introduces an acoustic survey database as an intermediary between the sensors and the triangulation process. The database stores propagation parameters recorded during preliminary surveys, which mediate the relationship between raw sensor data and final location determination, correcting for environmental distortions caused by urban structures
2Measurement precision
If more sensors are deployed to improve location accuracy, then measurement precision is improved, but system complexity and cost increase
Solution Approach 1:
The system changes parameters by recording and storing propagation characteristics (time delays, signal strengths, path identifiers) during preliminary acoustic surveys. These parameter changes enable the existing sensor array to achieve improved location accuracy through data processing rather than through adding more physical sensors, thereby reducing system complexity
3Area of stationary object
If sensors are spaced widely apart to cover large areas, then coverage area is improved, but location accuracy deteriorates due to increased triangulation errors
Solution Approach 1:
The system performs preliminary acoustic surveys that move the sound source through various locations within the wide coverage area, recording propagation paths to sensors spaced far apart. This preliminary characterization captures the relationship between widely-spaced sensors and various propagation paths, enabling accurate location determination despite large inter-sensor distances
4Measurement precision
If acoustic surveys are conducted to characterize propagation paths, then location accuracy is improved, but time and resources for system setup increase
Solution Approach 1:
The acoustic survey is conducted as a preliminary action during system deployment or periodic recalibration, characterizing propagation paths in advance. This one-time preliminary effort enables improved location accuracy for all subsequent gunfire detection operations, with the survey data stored in a database for rapid retrieval and application during operational detection
Solution Approach 2:
The system can perform acoustic surveys periodically to update propagation characteristics when environmental conditions change or to recalibrate the system. This periodic action maintains location accuracy over time without requiring continuous surveying during operational detection
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 method reduces location errors caused by refraction and blockage, enhances sensitivity determination, and enables accurate detection of gunfire even with fewer sensors, providing a dynamic coverage map and real-time system sensitivity assessment.
Implementation Method 1
buildings cause refraction, reflection, and blockage of audio waves propagating from gunfire to the various sensors
Implementation Method 2
buildings cause refraction, reflection, and blockage of audio waves propagating from gunfire to the various sensors
Implementation Method 3
audio waves propagating from gunfire to the various sensors
Data Source
AI summary
A survey method giving improvements in weapons fire location systems is disclosed. In an urban system with a distributed array in the midst of many buildings that block signal paths or create echoes, methods are provided to measure signal propagation. A survey or tour of the covered region uses a moving signal source to probe propagation inside the region. Survey results may indicate where more or fewer sensors are needed. Survey results plus current measured noise gives prediction of instantaneous system sensitivity. In addition, multipath propagation may be used to determine a location even when only one or two sensors detect the signal. In such exemplary cases, triangulation may be replaced or augmented by pattern recognition. Further, signals of the survey need not be acoustic impulses such as gunfire, but may be RF signals, or coded continuous signals so that gunfire-like sounds would not disturb citizens in the area.