Interpretation and Analysis of Recorded Gunshot Sounds

As submitted by the proposer: This project is an ongoing study of audio forensic gunshot acoustics applied to scientific interpretation and analysis of gunshot sounds and the effects of common digital recorders on these high-intensity sonic events. This research encompasses three major goals. First, the researchers increase the depth and applicability of published audio forensic knowledge via objective measurement of firearm acoustics under controlled, repeatable conditions. Second, the researchers will study and report upon the forensic interpretation limitations of common speech-channel personal recording devices, such as mobile phones, land-mobile radio, personal audio recorders, and audio data collected by emergency call center and dispatch center recording systems. Third, the researchers will assess the prospects for gunshot interpretation for recordings made in acoustically complex surroundings (effects of reflections, refraction, and reverberation). The proposed research involves two phases. In phase 1, the researchers will use the apparatus and methodology developed in their prior research (see Routh and Maher, 2016) on scientific and repeatable collection of firearm acoustical properties obtained anechoically (without early sound reflections), combined with simultaneous recordings by typical personal audio recording devices relevant to audio forensic investigations. In phase 2 the researchers will compare the objective recordings with the recordings from the personal audio recorders to evaluate the likelihood that forensically-useful information can be obtained from the personal audio recordings containing reflections, distortion, coding artifacts, and other non-ideal aspects. The researchers propose to assess methods for predicting gunshot sounds in acoustically complex surroundings of the real world, such as shots in the presence of nearby reflecting surfaces, vegetation, and terrain. The deliverables for this project include the phase 1 results: (i) additional cataloged results of firearm acoustical characteristics, and (ii) a comparative database of acoustical signatures from the personal recording devices. The phase 2 deliverables are: a systematic description of the strengths and weaknesses of personal audio recorders for close and distant gunshot recordings, and guidelines for audio forensic examiners in dealing with gunshot acoustical evidence from these non-scientific recording devices. Results will be published in scientific journals and trade publications, and the methodology and audio database will be provided to NIJ for dissemination. Note: This project contains a research and/or development component, as defined in applicable law, and complies with Part 200 Uniform Requirements - 2 CFR 200.210(a)(14). ca/ncf