Hawaii Voice Stress Analysis, Lie Detectors
|Polygraph Examination vs. Voice Stress Analysis
A polygraph (popularly referred to as a lie detector) is an instrument that
measures and records several physiological responses such as blood
pressure, pulse, respiration and skin conductivity while the subject is asked and
answers a series of questions, on the theory that false answers will produce
distinctive measurements. The polygraph measures physiological changes
caused by the sympathetic nervous system during questioning. Within the US
federal government, a polygraph examination is also referred to as a
psychophysiological detection of deception (PDD) examination.
The three most used systems in the human body that are recorded during a
- Respiratory activity is monitored by placing rubber tubes across the
- Electro dermal or "sweat gland" activity is recorded by placing two small
attachments to the fingers or palm of the hand;
- And cardiovascular activity is collected by a blood pressure cuff or similar
It is important to note that a polygraph does not include the analysis of
physiology associated with the voice. The use and effectiveness of the
polygraph is controversial, with the manner of its use and its validity subject to
increasing criticism. The credibility of the polygraph test is significantly
influenced by the operator's level of skill and professional expertise and the
subject's ability to alter their behavior and results.
Voice Stress Analysis (VSA)
Recently many police departments have become enamored with the latest
gadget for detecting lies, the voice stress analyzer.
The human voice is a complex instrument for expressing a full range of
emotional and cognitive states of mind, that even the best voice training in the
world cannot overcome. Vocal segments can be gathered and analyzed over
the phone, audio recording, or a face to face conversation.
Investigators using a computerized analysis of the speech flow can distinguish
between nonverbal emotional, cognitive and stressful elements within the
human voice and achieve a high level of testing credibility.
The technology enables an investigator to pinpoint the cause of stress, and
know whether it is caused by a lie, excitement, an exaggeration or cognitive
The human voice consists of six global levels:
- The Textual Level - the words we speak
- The Identifying Level - unique elements in every individual's voice
- The intonation level - the way we express ourselves
- The Emotional Level - an uncontrolled element of the voice that indicates
the level of excitement and the emotions they attach to what they are
- The cognitive Level - an uncontrolled element of the voice that indicates
the amount of conflict or agreement with the spoken sentence;
- The Physiological Element - indicates the stress physiological condition
Investigators can examine the six Levels with emphasis on the emotional,
cognitive and physiological patterns in the voice of a subject to deliver an
accurate message regarding vocal segments of a conversation or recording.
Studies Validating Voice Stress Analysis
(A Partial List)
1. Air Force Research Laboratory, Rome, NY, October, 2000. Funded by the National Institute of Justice, a three-year study by the AFRL
determined that voice stress analysis achieved an accuracy rate of 100% when used to detect stress in 45 known-conclusion
responses. (Available from http://extraafrl.af.mil/news/fa1100/features/detects:stress:feature.pdf)
2. Cestaro, V. Department of Defense Polygraph Institute, Ft. McClellan, AL. “A Comparison Between Decision Accuracy Rates
Obtained Using the Polygraph Instrument and the Computer Voice Stress Analyzer in the Absence of Jeopardy”, August, 1995. Cestaro
reports that “the lab simulations established that the CVSA performs electrically according to the manufacturer’s theory of operation”
and, even in the absence of jeopardy, which is a basic requirement in detection of deception, “These data indicate that there may be a
systematic and predictable relationship between voice patterns and stress related to deception” (Available from DoD web site: www.
3. Tippett, R. Florida Department of Law Enforcement. “Comparative Analysis Study of the Computer Voice Stress Analyzer and
Polygraph”, August, 1994. Both a polygraph and voice stress examiner, S/A Tippett examined 54 individuals that were convicted sex
offenders on probation and in treatment for their crimes. His conclusions were: “With these 54 examinations, there was a 100%
agreement between the CVSA and the polygraph. The number of examinees that were found to be deceptive (DI) were 35 and the
number of examinees found to be not deceptive (NDI) were 19. As a result of this study, it appears that the CVSA is as effective as
polygraph, which is the question this study set out to answer” (Available from University of Missouri web site: www.umr.
4. Ruiz, Legros, & Guell, 1990. Voice analysis to predict the psychological or physical state of a speaker. Published in Aviation, Space,
and Environmental Medicine, 1990. Ruiz et al. reports that their “research suggests that psychological stress may be detected as
acoustic modifications in the fundamental frequency of a speakers voice” and “that the fundamental frequency of the vocal signal is
slowly modulated (8-14 Hz) during speech in an emotionally neutral situation. In situations demanding increased ‘mental or
psychomotor’ activity, the 8-14 Hz modulation then decreases as the striated muscles surrounding the vocal cords contract in response
to the arousal, thus limiting the natural trembling” (Available from Library of Congress).
5. Chapman, J. Criminal Justice Department, Corning Community College, NY. “The Psychological Stress Evaluator As A Tool For
Eliciting Confessions”, 1989. Chapman selected 211 criminal responses at random from 2,109 known-conclusion responses where
voice stress analysis was used to test suspects. Professor Chapman’s study confirmed that voice stress analysis was accurate when
utilized as a truth verification device and produced a confession rate of 94.8% of the responses where deception was indicated
(Available from NITV).
6. Brockway, B.F., University of Colorado School of Nursing, Denver, Colorado. “Situational Stress and Temporal Changes In Self-
Report and Vocal Measurements.” Presented to the annual meeting of the American Association For the Advancement of Science,
February, 1977. Brockway’s study reports that voice stress analysis does depict predictable and self-reported anxiety (Available from
Library of Congress).
7. Smith, G.A. “Voice Analysis For Measurement Of Anxiety.” British Journal of Medical Psychology, 1977. The author concludes that
voice stress analysis is a valid measure of anxiety (Available from Library of Congress).
8. Borgen, L.A., Goodman, L.I., Parke-Davis Research Laboratories, Ann Arbor, MI. “Voice Stress Analysis of Anxiolytic Drug Effects.”
Results of the study indicated that voice stress analysis of the verbal responses correlated well with the other physiological responses
to acute stress (Available from Library of Congress).
9. Inbar, G.F., Eden, G. Dept. of Electrical Engineering Technion, Israel Institute of Technology, Haifa, Israel. “Psychological Stress
Evaluators: EMG Correlation With Voice Tremor” published in Biology of Cybernetics, 1976. Inbar and Eden were able to independently
verify the existence of the 8-14 Hertz ‘micro-tremor’ and to trace its origins to the central nervous system (Available from Library of
10. Wiggins, S.L., McCranie, M.L., and Bailey, P. Department of Psychiatry, Medical College of Georgia, Augusta, Georgia.
“Assessment of Voice Stress In Children”. Published in the Journal of Nervous Mental Disorders, 1975. The authors concluded that
“audio stress can be detected with a voice stress analyzer in psychiatric patients during the course of therapy and that the VSA could
serve as a useful tool for this purpose” (Available from Library of Congress).
11. Heisse, J. “Is The Micro-Tremor Usable? - The Micro-Muscle Tremor In The Voice.” U.S. House Subcommittee of the Committee
on Government Operations, 1974. Heisse analyzed 91 known-conclusion criminal responses utilizing voice stress analysis and
determined that “Audio stress analysis seems to be valid in detecting changes in various psycho physiological parameters so that a
trained examiner utilizing standard techniques can evaluate these changes and thus utilize the instrument in truth and deception”
(Available from Library of Congress).
12. Brenner, M. “Stage Fright and Steven’s Law.” Dept. of Psychology, Ohio State University, presented at the convention of the Eastern
Psychological Association, April, 1974. Brenner, utilizing a voice stress analyzer, established that the frequency of vocal stress
increased as a function of audience size (Available from Library of Congress).
13. Lippold, O. “Oscillations In The Stretch Reflex Arc And The Origin Of The Rhythmical 8-12 C/S Component Of The Physiological
Tremor.” The Journal Of Physiology, February, 1970. Lippold first discovers the physiological tremor in the human voice in the 8-12 Hz
range (Available from Library of Congress).
14. Lippold, O., Redfearn, J., Vuco, R. “The Rhythmical Activity Of Groups Of Muscle Units In The Voluntary Contraction Of Muscle.” The
Journal Of Physiology, August, 1957. Lippold, Redfearn and Vuco begin exploring the correlation between muscle activity and stress
(Available from Library of Congress).
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