Voice Stress Analysis
Detection of deception through measurement and analysis of voice characteristics. Voice stress analysis is an experimental technology that records psychophysiological stress responses in human voice.
How does voice stress analysis work?
A person experiences psychological stress when under pressure, for example, when being asked a question that instills fear of exposure. The consequences of lying and being exposed triggers a 'high stress' voice signature which the voice stress analyzer then records.
Verbal responses are processed through a computer utilizing proprietary software. The software detects, measures, and displays certain stress-related components of the voice. Superimposed on the audible voice frequencies are inaudible frequency modulations (FM) whose strength and pattern relate inversely to the degree of psychological stress in the speaker at the moment of utterance. These involuntary frequency modulations result from minute oscillations of the muscles of the voice mechanism.
Such oscillations, known as physiological tremor or micro-tremor, can be shown as a normal accompaniment to the activity of any voluntary muscle, occurring at a rate of 8-14 cycles per second. Most of the functional indicators of stress are attributed to the Autonomic Nervous System (ANS), micro-tremor in the voice mechanism is controlled by the Central Nervous System; as the ANS gains dominance in a stress situation, the micro-tremors are suppressed, and the FM in voice utterance is moderated or disappears.