Just Gunshot Acoustics Research_Special Release_014

This special release season of the 2017 NIJ R&D Symposium of Just Science, funded by the National Institute of Justice’s Forensic Technology Center of Excellence [Award 2016-MU-BX-K110], interviews Dr. Rob Maher. Below is the abstract submitted where Dr. Rob Maher explains his research: Gunshot acoustics–interpretation of the characteristic sounds produced by firearms recorded at a crime scene–is a specialization within the audio forensics field. Audio forensic evidence is increasingly common in law enforcement investigations because of the growing availability of inexpensive and lightweight digital voice recorders and miniature personal digital video camera systems for routine law enforcement and surveillance use. An increasing number of cases involving gunshot sounds are being captured in these audio recordings. The acoustical characteristics of a firearm depend upon the type of gun and ammunition, the distance and azimuth with respect to the gun barrel, and the acoustical reflections and reverberation due to nearby surfaces and objects. For scientific study it is necessary to separate the direct sound of the muzzle blast from the acoustic reflections, echoes, and reverberation that depend upon the recording environment. We use an elevated array of twelve specialized microphones capable of capturing the high intensity and short duration of the firearm’s muzzle blast concurrently over 180 degrees in azimuth. Each microphone is recorded with 16-bit resolution at a 500 kHz sampling rate, and the elevated platform allows the entire muzzle blast to be recorded before the arrival of the first acoustical reflection from the ground. This presentation includes a description of the firearm recording technique, the characteristics observed from these scientific recordings, recommendations on the use and processing of our database of firearm acoustical recordings, and a discussion of future prospects for forensic gunshot acoustical analysis.