Manifestations of Task-Induced Stress in the Acoustic Speech Signal

Abstract

In order to induce stress in an experimental subject, a task involving the addition of numbers under time pressure was developed. The subject was required to read six meters and to announce the sum of his readings, together with a test phrase. By controlling the duration of the meter display, the experimenter could vary the level of stress induced in the subject. For each of 10 subjects, numerous verbal responses were obtained while the subject was under stress and while he was relaxed. Contrasting responses containing the same test phrase were assembled into paired-comparison listening tests. Listeners could identify the stressful responses of some subjects with better than 90% accuracy and of others only at chance level. The test phrases from contrasting responses were analyzed with respect to level and fundamental frequency, and spectrograms of these test phrases were examined. The results indicate that task-induced stress can produce a number of characteristic changes in the acoustic speech signal. Most of these changes are attributable to modifications in the amplitude, frequency, and detailed waveform of the glottal pulses. Other changes result from differences in articulation. Although the manifestations of stress varied considerably from subject to subject, the test phrases of most subjects exhibited some consistent effects.

Vocal indicators of psychiatric treatment effects in depressives and schizophrenics

“…Roessler and Lester ( 1979) demonstrated such an energy shift when they compared the spectral energy distribution of a female voice in a low and high affective state. Hecker et al (1968) noted an increase in the amount of high-frequency energy in the glottal pulses when under stress. Support comes also from aviation research: Popov et al (1971) related increasing emotional stress as measured by heart rate to augmentation of the centroid of spectral energy between 300 and 1200 Hz.…”

“…Obviously the utterance of a neutral vowel requires the least articulatory effort compared with all other vowels. Hecker et al (1968) mentioned that under stress, subjects have a tendency to speak with a less constricted vocal tract which basically means that their articulatory effort becomes smaller. There is also evidence in the literature that depressive patients tend to speak with lax articulation (Newman and Mather, 1938).…”

Individual differences in cortisol stress response predict increases in voice pitch during exam stress

“…Indeed, an increase in voice pitch is the longest and most commonly reported finding in previous studies examining speech under stress (reviewed in Giddens et al, 2013;Kirchhübel et al, 2011). However, many studies have failed to replicate this finding (e.g., Dietrich and Abbott, 2012;Hecker et al, 1968;Johannes et al, 2000;Streeter et al, 1983;Tolkmitt and Scherer, 1986;Van Lierde et al, 2009). Others report an increase in minimum voice pitch or a decrease in its standard deviation (F0 sd), with no systematic change in mean pitch (Park et al, 2011;Tolkmitt and Scherer, 1986).…”

“…Alternatively, as has been suggested by many researchers, these inconsistencies in previous work may be tied to variation in the severity of the stress response, wherein vocal changes may be observed only in particular contexts (e.g., natural stress scenarios) or among individuals surpassing a critical threshold of stress (Beatty and Behnke, 1991;Johannes et al, 2000;Kirchhübel et al, 2011;Scherer, 1979). Despite this parsimonious possibility, only a handful of studies examining speech under stress have controlled for individual differences in stress levels (Hecker et al, 1968;Sigmund, 2006) or in participants' propensity toward anxiety (Beatty and Behnke, 1991;Tolkmitt and Scherer, 1986).…”

“…However, this may not apply to analysis of verbal parameters, such as articulatory and prosodic patterns in stressed speech (see e.g., Hecker et al, 1968;Ruiz et al, 1996;Tolkmitt and Scherer, 1986). …”