NCJ Number
14788
Date Published
1972
Length
45 pages
Annotation
THE VOICE ANALYZER IS AN ELECTRONIC DEVICE WHICH EXTRACTS SPEECH PARAMETERS FROM THE SPOKEN WORD TO DETERMINE WHETHER AN INDIVIDUAL IS UNDER STRESS AT THE TIME OF HIS SPEAKING.
Abstract
TESTS SHOWED THAT KNOWN LIE RESPONSES TO A QUESTION CAUSED A SHIFT IN THE TOTAL AMOUNT OF ENERGY PRESENT IN THE FREQUENCY RANGES OF 100-120 AND 600-800 CYCLES PER SECOND OF AN INDIVIDUAL'S SPEECH SIGNAL. THIS PROJECT TESTED A PROTOTYPE VOICE ANALYZER BY ANALYZING NUMEROUS TAPE RECORDINGS OF SUBJECT INTERROGATIONS FOR ACTUAL AND STAGED CRIMES. THESE INTERROGATIONS WERE GROUPED INTO TWO MAJOR CATEGORIES. THE 'PEAK-OF-TENSION TESTS' WERE DESIGNED SUCH THAT A SUBJECT, ASKED THE SAME QUESTION CONCERNING A NUMBER OF SIMILAR ITEMS, WAS EXPECTED TO REACT TO ONLY ONE OF THESE QUESTIONS AS EVIDENCED BY A POLYGRAPH. IN THE 'ZONE OF COMPARISON TEST' RESPONSES TO INNOCUOUS QUESTIONS WERE COMPARED TO RESPONSES TO QUESTIONS EXPECTED TO EVOKE A STRESSFUL RESPONSE. RESULTS OF THE VOICE DATA ANALYSES ARE DISCUSSED IN DETAIL. IT WAS FOUND THAT THE PROTOTYPE VOICE ANALYZER, WHEN USED WITH THE ZONE OF COMPARISON PROTOCOL, PROVIDES AN EFFECTIVE MEANS OF ASSESSING GUILT OR INNOCENCE WITH HIGH CONFIDENCE. SCHEMATIC DRAWINGS OF THE PROTOTYPE CIRCUITS AND EQUIPMENT ARE ALSO INCLUDED, ALONG WITH A DESCRIPTION OF THE SIGNAL FLOW THROUGH THE CIRCUITS. THE INTERROGATION AND ASSESSMENT PROTOCOLS FOR USE OF THE VOICE ANALYZER ARE ALSO SUMMARIZED.