Newswise — Lie detectors are used commonly by police departments throughout the United States as a tool to help detect deception based on bodily responses to stress, such as pulse and breathing rate, that are relayed by sensors attached to the suspect,. However, sensitivity is limited and the sensors can be fooled by simple techniques well described on a variety of websites.
But by evaluating the acoustical properties of the human voice, a research team at the University of Florida, Gainesville, is expanding the scientific understanding of the physics of vocal stress – insight that might one day be used to improve the detection of deception. The research team confirmed that the human voice changes in systematic and perceptible ways under carefully measured, significant stress levels. One early surprise finding is that men and women respond differently to the same stressors. The group will present its work at the 162nd Meeting of the Acoustical Society of America in San Diego on Nov. 2, 2011.
"In male subjects, higher degrees of physiological arousal were under-reported – what you might call a ‘tough guy’ response," explains lead researcher, James Harnsberger, Ph.D., a speech scientist in the Department of Linguistics. The idea to test for gender difference was not part of the original study design. A graduate student on the project, Christian Betzen, suggested analyzing separately the gender categories for the four stress metrics used in the study – two physical and two self-reporting. “The results were a surprise. We had expected that higher stressors would prompt both increased physiological response and increased self-reported stress levels in all test subjects fairly uniformly for both men and women,” Dr. Harnsberger explains. One early conclusion these data suggest is that acoustic analyses should include gender in the study design.
In the study, the Florida team enrolled study subjects from community or religious groups who were considered “committed” – that is, strongly affiliated with a group identity. The study subjects were audio-visually recorded while coached by the researchers to vocalize both truthful and deceptive statements – with the threat from the researchers that the recordings would be shown to fellow community members for judgment. In some conditions, stress was also induced by the administration of electric shock at levels calibrated by the individual volunteer. Other stress responses were measured by pulse rate, skin conductance level (due to sweat), pulse rate, and two self-report scales of perceived discomfort.
Over time, studies such as this hold promise for improving a variety of speech analysis systems in a range of settings – from lie detectors to computerized voice recognition. This is because the acoustic properties of stressed speech overlap with acoustic properties of speech that are dependent on such variables as the speaker’s unique identity, his emotional state, and the words he produces.
The paper 3aSCb44, “Talker and gender effects in induced, simulated, and perceived stress in speech,” will be presented Wednesday morning, Nov. 2.
Main meeting website: http://acousticalsociety.org/
Searchable index: http://asa.aip.org/asasearch.html
Hotel site: http://www.towncountry.com/index.cfm
Webcast registration and viewing: http://www.aipwebcasting.com
WORLD WIDE PRESS ROOM
In the week before the meeting, the ASA's World Wide Press Room (www.acoustics.org/press) will be updated with lay-language papers, which are 300-1200 word summaries of presentations written by scientists for a general audience and accompanied by photos, audio, and video.
ABOUT THE ACOUSTICAL SOCIETY OF AMERICA
The Acoustical Society of America (ASA) is the premier international scientific society in acoustics devoted to the science and technology of sound. Its 7,000 members worldwide represent a broad spectrum of the study of acoustics. ASA publications include The Journal of the Acoustical Society of America (the world's leading journal on acoustics), Acoustics Today magazine, books, and standards on acoustics. The society also holds two major scientific meetings each year. For more information about ASA, visit our website at http://www.acousticalsociety.org.