NCJ Number
105299
Journal
Champion Dated: (April 1986) Pages: 6-8,10-13
Date Published
1986
Length
7 pages
Annotation
This article discusses the enhancement, transcription, authentication, comparison, and matching of tape recordings associated with electronic surveillance.
Abstract
Enhancement, which involves making poorly recorded audio tapes more intelligible, is a process of selective filtering using an analog filter and equalizer, the automatic digital filter, and assorted recording and electronic components. The production of an accurate transcript from an audio recording depends on audio quality after enhancement and the skill of the stenographer. Tape authentication involves an analysis for signs of tampering and alteration. Authentication is based on the authenticator's knowledge of the characteristics of audio tape and recording machines. Waveform and photographic-impression analysis of erase head and record head start-stop impressions can identify the machines used to record sound on an original tape. A comparison of voice prints consists of matching the characteristics of a voice on one tape to a sample recorded under controlled conditions, based on an analysis of voice sound characteristics. Matching the audio of one location to a known sample permits the identification of the location of the recording at issue based on the cyclical identification of sounds characteristic of particular locations. 5 figures and 33 footnotes.