Page 24 - Summer 2015

Robert C. Maher
Postal:
Department of Electrical and Computer Engineering Montana State University 610 Cobleigh Hall Bozeman, Montana 59717-3780 USA
Email:
rob.maher@montana.edu
Lending an Ear in the Courtroom: Forensic Acoustics
Forensic acoustics deals with acquisition, analysis, and evaluation of
audio recordings to be used as evidence in an official legal inquiry.
Figure 1. A typical courtroom, as pictured here, may differ in many respects from venues such as the class- rooms and professional conference halls more familiar toASAmembers,butacousticalforensicsciencecanplay a key role in both civil and criminal legal proceedings.
Introduction
In most circumstances, the memorable sounds of the world around us include the routine and ephemeral sounds of civili- zation in our urban or rural sur- roundings; the sociable speech of friends and coworkers; the pleasurable notes of music; and the occasional barks, chirps, croaks, purrs, and thunderous rumbles of the biophony and geophony. However, there are some circumstances in which the sounds around us become the subject of a law enforce-
ment investigation, an accident review, or some other legal proceeding that ends up in a courtroom. Although most acousticians might reasonably prefer to stay out of a courtroom (Figure 1), except perhaps to improve the architectural acoustics of the facility, there are surprisingly many circumstances in which the knowledge of acoustical scientists can be helpful to legal and investigative proceedings.
• Does your coworker's voice mail message confess to a crime?
• Was the emergency alarm actually loud enough to be heard when the
engine was running?
• Was that subtle background sound due to a telltale malfunction emerging
in your passenger plane’s airframe?
• Does that music playing in the bar infringe on a valid copyright?
• Was the threatening message on your voice mail the utterance of
Mr. Smith or was it Mr. Jones?
Welcome to the Field of Forensic Acoustics!
Forensic science has become a common subject in the media due to dramatic court cases in the news and the emergence of fictional entertainment series on US televi- sion like CSI: Crime Scene Investigation and NCIS on the CBS network and quasi documentaries such as Forensic Files on the TLC and Headline News networks. Even the rather arcane specialty of audio forensics sometimes finds its way into the headlines, particularly in sensational cases. Many people listened to online copies of the 911 call center audio evidence related to the tragic shooting of un- armed black teenager Trayvon Martin in 2012, and recent reports have described the recovery and interpretation of cockpit voice recorder “black box” audio from
22 | Acoustics Today | Summer 2015, volume 11, issue 3 ©2015 Acoustical Society of America. All rights reserved.