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Advancing Audio Forensics of Gunshot Acoustics

NCJ Number
251608
Date Published
Author(s)
Robert C. Maher
Agencies
NIJ-Sponsored
Publication Type
Research (Applied/Empirical), Report (Study/Research), Report (Grant Sponsored), Program/Project Description, Grants and Funding
Grant Number(s)
2014-DN-BX-K034
Annotation
In addressing the need for improved scientific understanding of audio forensic evidence, particularly the analysis and interpretation of recorded gunshot sounds, the primary goal of this research was to create an apparatus and methodology for scientific and repeatable collection of firearm acoustical properties recorded without early sound reflections (anechoically).
Abstract
The project succeeded in obtaining good, repeatable gunshot recordings by using the specialized audio recording equipment and the standardized firearm test procedure. Researchers designed, built, and implemented a test rig that contained omnidirectional instrumentation microphones placed at 15-degree intervals on a semi-circular arc of 3-meter radius. A high-speed multichannel digital audio recorder served each microphone. Each firearm tested was fired from the center of the arc while the microphone system simultaneously and synchronistically recorded the acoustical wave forms from each angular position. The project involved the following seven components: 1) assembling and testing the microphone mounting system; 2) performance of the first round of gunshot recordings; 3) analysis of the new recording for consistency and reliability; 4) analysis of shot-to-shot variability; 5) analysis of muzzle-blast duration; 6) comparison of signal level as a function of azimuth and selected firearm; and 7) initial work on modeling and identification. It is now critical for forensic examiners in their gunshot interpretation to understand the strengths and weaknesses of the audio recording systems used in mobile audio recorders, particularly the miniature digital voice recorders carried by many law enforcement officers. 9 figures, listings of 8 scholarly products and 4 layman's articles, and the website for the database
Date Created: April 30, 2018