Vocal Spectrum Research Articles

Detecting Deception: The Promise and the Reality of Voice Stress Analysis

Within the past decade a number of so-called voice stress analyzers have been marketed for law enforcement and forensic science purposes. These devices are said to extract from the vocal spectrum a subaudible microtremor signal that is useful in detecting stress in a speaker's voice; thus, it is claimed these devices have great utility as lie detectors and are as accurate as the traditional polygraph instrument. A review of the evidence now accumulated about these devices shows that the evidence for the existence of a microtremor in the voice is problematic and that the capability of these devices in detecting stress is equally questionable. Without exception, however, the scientific evidence reported to date shows that voice stress analyzers are not effective in detecting deception; none of these devices has yet been shown to yield detection rates above chance levels in controlled situations. A brief comparison of voice stress analysis and polygraphic testing as methods of lie detection is made.

Acoustic analyses of potential vocalization in lambeosaurine dinosaurs (Reptilia: Ornithischia)

Lambeosaurine dinosaur crests are judged to have been conducive to resonation on the basis of an acoustic analysis of the structure of the nasal cavity. Size and shape of the nasal cavity suggest low vocal frequencies in adults, as does information on potential auditory acuity in these animals. Lateral diverticula (present in all but juvenile specimens) acted to suppress portions of the vocal spectrum. Juveniles vocalized at higher frequencies than adults and potential auditory sensitivity at high frequencies in adults suggests a high degree of parent-offspring vocal communication. Sexual variation and causes of selection for low frequency vocalization are also examined.

Vocal cry analysis in dairy goats

The vocal outputs of two adult twin goats and their twin off-spring indicate that capra vocal behavior can be grouped into two main call types, that is, orienting bleats and distress bleats. The former is characterized as essentially a closed velar vocalization emitted primarily through the mouth. Most of the energy is below 4 kHz with maximal peaks at 360 Hz (F0), 1250 Hz, and 2500 Hz. The distress bleat is characterized by both oral and nasal emission with energy up to 15 kHz. There is peak energy at 360 Hz (F0), 2500 Hz (primarily), 8100 Hz, and 11 000 Hz. Kid vocalizations were sampled periodically for the first six months of life. Again an orienting and distress bleat can be differentiated. Basically, the orienting bleat is characterized by energy below 5700 Hz with peak levels at F0, 700 Hz, and 3800 Hz. The distress bleat has energy up to 15 kHz with an additional peak at 8800 Hz. Fundamental frequency was found to vary with age not only in range but in contour. The maternal filial relationship will be discussed, suggesting that the mother's poor auditory ability to recognize her kid during the first days of life is a function of essentially identical vocal spectrum of kid bleats during this period.

Voice prints in laryngeal disease.

The scientific merit of sound spectrography has been well established for the study of vocal pathology. Contour display spectrography provides even better visualization of the vocal spectrum. Voice prints permit an objective evaluation of the acoustic correlates of hoarseness, and suggest a valuable new technique for the acoustic identification of different laryngeal diseases.

Comparison of the Spectra of the Voices of Twins

Differences between identical and fraternal twins have long been examined in attempts to separate characteristics determined by nature from those resulting from nurturing. This paper describes a study of the vocal spectra pairs of monozygotic, dizygotic, and nontwin age- and sex-matched controls. The results are based on a statistical comparison of the relative energy of the voices of pairs of individuals at each of a number of spectral points. The monozygotic twin pairs were found to be significantly more alike in the range from 670 to 2000 cps but not in the range below 400 cps. These data are consistent with previous findings in this laboratory that the lower-frequency range is more sensitive to changes that accompany emotion-evoking stimuli. Thus, the lower section of the spectrum is more variable whereas the higher section is more stable. The data support the hypothesis that the vocal spectrum is, at least in part, determined by genetic factors. [This research was supported by Public Health Service grant MH-04664, U. S. Department of Health, Education, and Welfare.]

La voce nei gemelli monozigotici

SUMMARYThe Authors describe the methodology of an analytic electroacoustical study of the spoken voice of MZ twins of prepuberal age.The study was intended to reveal any possible analogies of the vocal spectrum and to ascertain the extent of the genetic conditioning of such analogies. For this purpose the Authors analyzed electroacustically a recorded material obtained as follows:a) during free conversation,b) by applying a laryngophone to the larynx in order to identify the fundamental laryngeal frequency,c) after introducing in both cotwins a critical variant by application to the ears of a deafening tone.Identical studies were carried out on a control material including DZ pairs and pairs of random-coupled non-related individuals very similar as to age and build.The results can be summed up as follows:1. The curves representing the vocal spectrum at the various frequency for each MZ pair reveal a marked similarity both in the general trend of the vocal curve and in the values at each point of the curve. The similarity is specially marked in the vicinity of the voice's fundamental frequency.2. The location of the fundamental laryngeal frequency in the majority of MZ pairs has been found to be very close, and in many cases even coincidental.3. Neither the analogies in the vocal spectrum nor the location of the fundamental frequency have been significantly modified by deafening.4. The control material (including DZ pairs and random-coupled pairs of individuals having different heredity but similar as to age and build) has revealed marked dissimilarities both in the curves of the vocal spectrum and in the location of the fundamental laryngeal frequency.On the basis of these results the Authors conclude that there is a similarity in the spoken voice of MZ pairs of prepuberal age they have examined, and this similarity is to be largely ascribed to morphological and functional factors of similarity of a genetic nature in the laryngeal generator.