The evolution of speech: a comparative review

Body weight, length, and vocal tract length were measured for 23 rhesus macaques (Macaca mulatta) of various sizes using radiographs and computer graphic techniques. Linear predictive coding analysis of tape-recorded threat vocalizations was used to determine vocal tract resonance frequencies (“formants”) for the same animals. A new acoustic variable is proposed, “formant dispersion,” which should theoretically depend upon vocal tract length. Formant dispersion is the averaged difference between successive formant frequencies, and was found to be closely tied to both vocal tract length and body size. Despite the common claim that voice fundamental frequency (F0)provides an acoustic indication of body size, repeated investigations have failed to support such a relationship in many vertebrate species including humans. Formant dispersion, unlike voice pitch, is proposed to be a reliable predictor of body size in macaques, and probably many other species.

/pdf/vocal-tract-length-and-formant-frequency-dispersion-2vtop2z15t.pdf

Vocal tract length and formant frequency dispersion correlate with body size in rhesus macaques

Calls out of chaos: the adaptive significance of nonlinear phenomena in mammalian vocal production

Manipulations of fundamental and formant frequencies influence the attractiveness of human male voices

1. Introduction When autumn arrives in northern Europe, female red deer (Cervus elaphus L.) begin to congregate. The mating season has begun. They are soon joined by males, who have spent the previous ten months in preparation, feeding and sparring. Some of the males herd females into groups or "harems", which they vigorously defend from other males. A prominent component of this defense is roaring, a powerful, low-pitched groaning sound made only by males, and primarily by harem holders. Why do males produce these sounds, and what effect do they have on listeners? Early observers (Darling 1937) suggested that the roars intimidated rivals, and repelled intruders without the need for a dangerous fight. However, selection should favor opponents who are not so easily intimidated, and who base their behavior solely upon a balanced assessment of their chances of winning a fight and inheriting the herd (Maynard Smith and Price 1973). In a classic paper, Clutton-Brock and Albon (1979) showed that roaring provides a source of information relevant to this decision: roaring rates of individual males are highly correlated with their fighting ability and thus provide an accurate indication of the males' ability to repel intruders. They also demonstrated, in a series of playback experiments, that rival males attend to this information, responding preferentially to high roar rates and ignoring the roars of young, small males. Red deer roaring has since become a classic example of "truth in advertising" in an animal vocalization.

https://link.springer.com/content/pdf/10.1007%2F0-387-22762-8_3.pdf

Unpacking “Honesty”: Vertebrate Vocal Production and the Evolution of Acoustic Signals

The purpose of this investigation is to shed some more light on the conflicting views about a number of acoustic parameters which might carry information on some general somatic features of the speake

How Well Does Average Fundamental Frequency Correlate with Speaker Height and Weight

Speech scientists often have to work with speech signals that have been transmitted over the telephone. Although the acoustic properties of telephone transmission such as the band-pass filter characteristics are well known, little attention has been paid to their effect on the measurement of speech parameters. This study deals with artefacts introduced by the lower cut-off slope of the transmission channel on vowel formants. For theoretical reasons, frequency components may be assumed to be attenuated the lower they are. Therefore F1 of most vowels can be expected to be affected most. Attenuation of the lower components of a formant will necessarily increase the relative weight of the higher components for the determination of a formant and thus cause an artificial upward shift of its centre frequency. An empirical investigation with directly and telephone-transmitted samples from ten male and ten female subjects shows that the predicted effect on F1 does in fact occur for all tested vowels except /a/, whose F1 is too high to be affected by the slope of the band-pass. The consequences of measurement errors arising from such artefacts are discussed with special reference to speaker identification and empirical dialectology.

Beware of the ‘telephone effect’: the influence of telephone transmission on the measurement of formant frequencies

Patterns of voice disguise in forensic cases involving speaker identification or speaker profiling may contain clues to features of the undisguised voice of a speaker. In a longitudinal and synchronous study, 100 subjects were asked to read a text on five occasions during a period of six months, first using their normal voices, and subsequently with two out of three modes of voice disguise, (1) raising fundamental frequency, (2) lowering fundamental frequency, (3) denasalization by firmly pinching theirnose. The focus of this investigation is on fundamental frequency (F0). Results show that most subjects were in fact able consistently to change their F0 according to the mode of disguise they had selected. However, there were differences between both sexes with regard to their preference of disguise modes as well as to the individual articulatory ‘strategies’ which they employed to implement them. Results corroborate experience with forensic casework, that is, they show that there is a constant relation between the F0 of a speaker’s natural speech behaviour and the kind of disguise he willuse in an incriminating phone call. Speakers with higher-than-average F0 tend to increase their F0 levels. This process may or may not involve register changes from modal voice to falsetto. Speakers with lower-than-average F0 prefer to disguise their voices by lowering F0 even more and often end up with permanently creaky voice. Thelatter trend can be observed much more clearly in males. Females are generally more reluctant to make drastic changes to their fundamental frequency patterns.

Effects of voice disguise on speaking fundamental frequency

The comparability and compatibility of speech samples is of paramount importance to modern techniques of forensic speaker identification. This principle applies also to factors commonly referred to as speaking tempo, speech rate, speed of utterance, and the like, which may differ considerably as a function of various characteristics of the speaking situation. Consider, for example, a blackmailer's telephone call to a victim, i.e. a spontaneous text, often produced in a dialogic situation, and, on the other hand, a text (even the same text) read aloud from a transcript by a suspect and recorded directly over a microphone in a police station. With respect to speaking tempo the compatibility problem is enhanced by the fact that, other than, for instance, F0 and pitch, it cannot be attributed to a single phonetic parameter on the level of either production or perception. In this study the influence of a number of temporal variables which have been associated with speaking tempo in the literature have been investigated in three speaking conditions considered typical of the forensic setting. Furthermore, the potential influence of the telephone recording situation was investigated, a characteristic feature in the vast majority of speaker identification cases. Results from ten speakers and fifteen listeners indicate that speaking condition but not recording condition does in fact have an influence on speaking tempo in terms of both production and perception, with syllable rate, or rather the amount of pausing contained in this parameter, being the best temporal correlate. On the other hand, articulation rate remains almost entirely unaffected and is also remarkably constant within speakers. Therefore it may be regarded as a promising speaker-specific parameter for forensic speaker identification.

Some general phonetic and forensic aspects of speaking tempo

Automatic speaker recognition systems typically rely on parameters derived from resonance features of the vocal tract. Th is implies that the more similar the geometry of two vocal tracts is, the more similar will be the respective similarity coeffi cients, or likelihood ratios (LRs). Quite obviously this problem is particularly relevant to related speakers, most extremely for identical (monozygotic) twins. Th is paper is about an experiment with 9 male and 26 female pairs of identical twins who produced one read and one spontaneous speech sample. An automatic system for forensic speaker recognition (Batvox 3.1) was used to calculateinter-speaker (non-target), (2) intratwin pair, and (3) intra-speaker (target) LR distributions. Results show that in certain conditions an automatic Bayesian-based system is capable of distinguishing even the vast majority of very similar sounding voices such as those of identical twins. However, the performance of the system used here was superior for male as compared
to female voices. Quite obviously the sex-related diff erence was enhanced by the genetic similarity factor.

Hermann J. Künzel

Papers

How Well Does Average Fundamental Frequency Correlate with Speaker Height and Weight

Beware of the ‘telephone effect’: the influence of telephone transmission on the measurement of formant frequencies

Effects of voice disguise on speaking fundamental frequency

Some general phonetic and forensic aspects of speaking tempo

Automatic Speaker Recognition of Identical Twins