Effects of Alcohol on the Acoustic‐Phonetic Properties of Speech: Perceptual and Acoustic Analyses

Abstract

This report summarizes the results of a series of studies that examined the effects of alcohol on the acoustic-phonetic properties of speech. Audio recordings were made of male talkers producing lists of sentences under a sober condition and an intoxicated condition. These speech samples were then subjected to perceptual and acoustic analyses. In one perceptual experiment, listeners heard matched pairs of sentences from four talkers and were required to identify the sentence that was produced while the talker was intoxicated. In a second perceptual experiment, Indiana State Troopers and college undergraduates were required to judge whether individual sentences presented in isolation were produced in a sober or an intoxicated condition. The results of the perceptual experiments indicated that groups of listeners can significantly discriminate between speech samples produced under sober and intoxicated conditions. For acoustic analyses, digital signal processing techniques were used to measure acoustic-phonetic changes that took place in speech production when the talker was intoxicated. The results of the acoustical analyses revealed consistent and well-defined changes in speech articulation between sober and intoxicated conditions. Because speech production requires fine motor control and timing of the articulators, it may be possible to use acoustic-phonetic measures as sensitive indices of sensory-motor impairment due to alcohol consumption.Alcohol is generally considered to be a central nervous system depressant. Medium and high blood concentrations of alcohol have been found to impair intellectual functioning, reaction time, coordination, reflexes, and nerve transmission. 1 Alcohol consumption is also thought to produce changes in speech production that are often described as "slurred speech." Changes in speech production after alcohol consumption are often used by law enforcement personnel, bartenders, and others as general indices of motor impairment due to alcohol intoxication. Changes in speech production have also been used as a sign of impairment due to other drugs. Shagass 2 related slurring of speech to the initial threshold of consciousness impairment produced by sodium amythal. Very little research, however, has explored the nature of acoustic-phonetic changes in the speech waveform due to alcohol intoxication. Because speech production requires fine motor control, timing, and coordination of the articulators, it may be possible to use acoustic-phonetic measures as sensitive indices of impairment due to alcohol intoxication.Some research relevant to this problem has been conducted. Several studies have examined the general effects of alcohol on speech production. Moskowitz and Roth 3 examined the effects of alcohol on response latency in a picture-naming task. Thirty pictures of words chosen from a word frequency list were named by 12 subjects while sober and after consuming a beverage designed to achieve a blood alcohol concentration (BAC) in the range

Do Voice Recordings Reveal whether a Person Is Intoxicated? A Case Study

“…They also found a change in the long-term average spectrum in intoxicated speech. There was an increase in highfrequency energy, which may reflect, in addition to an increase in the harmonics-to-noise ratio, an increase in the unvoiced/ voiced ratio (the ratio of the number of frames classified as voiceless and the number of frames classified as voiced) after alcohol consumption [as reported by Pisoni and Martin, 1989]. Finally, all previous studies which included relevant measures have found that speaking rate decreases (segmental durations increase) after alcohol consumption.…”

“…Trojan and Kryspin-Exner [1968] reported an increase in fundamental frequency (F 0 ). Pisoni and Martin [1989] found that F 0 decreased for some, but not all subjects. Klingholz et al [1988] also found a tendency for decreased F 0 .…”

“…Klingholz et al [1988] also found a tendency for decreased F 0 . F 0 is also more variable in speech produced while intoxicated when compared to a control condition [Pisoni and Martin, 1989;Klingholz et al, 1988]. As will be noted below, there are two possible sources for this increased variability.…”

“…For more complete reviews of the literature see Pisoni et al [1986], Klingholz et al [1988], and Pisoni and Martin [1989]. The effects of alcohol on speech production that have been observed in controlled laboratory studies can be divided into three types: gross effects, segmental effects and suprasegmental effects.…”

About forensic phonetics

“…Prior to the work of the present author, the relationships between speech and intoxication appeared to be that: 1) speaking fundamental frequency (SFF) level was often lowered and SFF variability sometimes increased, 2) speaking rate was reduced, 3) the number and length of speech pauses often increased and 4) speaking intensity levels sometimes were lowered (Chin/Pisoni 1996;Pisoni/Martin 1989). Again, however, virtually all of these alcohol-speech relationships were quite variable.…”