Digital signal processing in forensic acoustics cases

Abstract

Forensic acoustics typically considers speaker identification, authenticity analysis, audio enhancement and transcript verification by analyzing and processing audio or speech signals. Other applications in forensic acoustics include different analyses of non-speech audio signals. This presentation will discuss three contentious litigation cases in which various digital processing techniques formed the foundation of scientifically-based conclusions. The first is a products liability case involving the death of a firefighter and his Personal Alert Safety System. When movement of a firefighter ceases, a high-pitched audible alert is emitted. When numbers of these devices were recorded, the task was to determine if the deceased firefighter’s device was included within the multiple devices examined. In the second case the order of the discharges of various caliber weapons based on a 9-1-1 call was determined via digital signal processing. The third study utilized processing techniques to differentiate and identify the type of sounds produced in a number of murder trials. These cases represent the varied challenges in forensic audio and acoustics investigations, and show the difficulty of applying broad theory to practice, the necessity for innovation in the field and the basis for establishing scientific reliability in order to secure admissibility into the courtroom.