Vocal production mechanisms in a non-human primate: Morphological data and a model

Institut für Theoretische Biologie, Humboldt-Universität zu Berlin, Invalidenstrasse 43, 10115 Berlin, Germany.
Journal of Human Evolution (Impact Factor: 3.73). 02/2005; 48(1):85-96. DOI: 10.1016/j.jhevol.2004.10.002
Source: PubMed

ABSTRACT Human beings are thought to be unique amongst the primates in their capacity to produce rapid changes in the shape of their vocal tracts during speech production. Acoustically, vocal tracts act as resonance chambers, whose geometry determines the position and bandwidth of the formants. Formants provide the acoustic basis for vowels, which enable speakers to refer to external events and to produce other kinds of meaningful communication. Formant-based referential communication is also present in non-human primates, most prominently in Diana monkey alarm calls. Previous work has suggested that the acoustic structure of these calls is the product of a non-uniform vocal tract capable of some degree of articulation. In this study we test this hypothesis by providing morphological measurements of the vocal tract of three adult Diana monkeys, using both radiography and dissection. We use these data to generate a vocal tract computational model capable of simulating the formant structures produced by wild individuals. The model performed best when it combined a non-uniform vocal tract consisting of three different tubes with a number of articulatory manoeuvres. We discuss the implications of these findings for evolutionary theories of human and non-human vocal production.

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Available from: Klaus Zuberbühler, Sep 27, 2015
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    • "Thus, the sagittal distances measured in our three anaesthetized Diana monkeys are likely to represent a reasonable estimate of the area function of the monkeys' vocal tract. Nevertheless, we agree with Lieberman that more sophisticated techniques capable of documenting the vocal tract changes in vocalizing animals are desirable for future studies (Riede et al., 2005). "
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    ABSTRACT: Male West African Diana monkeys (Cercopithecus diana) produce acoustically distinct alarm calls to two of their main predators, the crowned eagle and the leopard. The calls are re-markable in their acoustic structure for at least three reasons. First, they exhibit clear formant frequencies, a defining feature of human speech. Second, Diana monkeys are able to modify the basic structure of these formants by creating formant tran-sitions. In leopard alarm calls, the first formant describes a transition of approximately 150 Hz, while the transition of the second one is about 200 Hz. In striking contrast, the two formants remain relatively constant in eagle alarm calls (Riede and Zuberbühler, 2003a,b). Experiments have shown that these acoustic differences have semantic value to recipients (Zuber-bühler, 2003). Third, the first and second formants in Diana monkeys' alarm calls are in close proximity, a feature not nor-mally observed in animal vocalizations. We propose that this formant proximity is the result of a discontinuity (or 'non-uni-formity') along the monkey's vocal tract. In a previous paper (Riede et al., 2005), we sought to un-derstand the production mechanisms of the Diana monkey vocal system using a computer modelling technique, based on anatomical data. Lieberman (2006) has challenged a num-ber of our findings. His concerns relate to the possibility of tongue movements, pharyngeal constrictions, and the posi-tion of the larynx. Additionally, the technique of deriving vocal tract area functions from lateral x-rays is criticized. We would like to respond to these criticisms by first sum-marizing our main point, the notion of non-uniform vocal tracts in nonhumans, before responding in detail to Lieber-man's critique.
    Journal of Human Evolution 10/2014; 50(2):222-225. DOI:10.1016/j.jhevol.2005.10.005 · 3.73 Impact Factor
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    • "Human sopranos change the mouth opening to move F 1 in synchronization with f 0 as the latter changes. The vocal apparatus moves flexibly during vocalizations in nonhuman primates (Fitch, 2000b; Riede et al., 2005) rather than remaining static as previously thought (Lieberman et al., 1969), and gibbons indeed open their mouths wider in synchrony with rising pitch (Haimoff, 1984). Furthermore, gibbons might voluntarily regulate movements of their vocal apparatus to perform such synchronized movements (e.g., through the audio feedback ). "
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    ABSTRACT: Diversifications in primate vocalization, including human speech, are believed to reflect evolutionary modifications in vocal anatomy and physiology. Gibbon song is acoustically unique, comprising loud, melodious, penetrating pure tone-like calls. In a white-handed gibbon, Hylobates lar, the fundamental frequency (f(0) ) of song sounds is amplified distinctively from the higher harmonics in normal air. In a helium-enriched atmosphere, f(0) does not shift, but it is significantly suppressed and 2f(0) is emphasized. This implies that the source is independent of the resonance filter of the supralaryngeal vocal tract (SVT) in gibbons, in contrast to musical wind instruments, in which the filter primarily determines f(0) . Acoustic simulation further supported that gibbons' singing is produced analogously to professional human soprano singing, in which a precise tuning of the first formant (F(1) ) of the SVT to f(0) amplifies exclusively the f(0) component of the source. Thus, in gibbons, as in humans, dynamic control over the vocal tract configuration, rather than anatomical modifications, has been a dominant factor in determining call structure. The varied dynamic movements were adopted in response to unique social and ecological pressures in gibbons, allowing monogamous gibbons to produce pure-tonal melodious songs in the dense tropical forests with poor visibility. Am J Phys Anthropol, 2012. © 2012 Wiley Periodicals, Inc.
    American Journal of Physical Anthropology 11/2012; 149(3):347-55. DOI:10.1002/ajpa.22124 · 2.38 Impact Factor
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    • "A computational model of the vocal tract is a mathematical representation of the luminal areas of the supralaryngeal tract with the boundaries of the internal organs and tissues. Two studies have used computational models to show that spectral prominences of nonhuman primate vocalizations were formants (Cercopithecus diana: Riede et al. 2005; Varecia variegate: Gamba and Giacoma 2006). However, the explanatory potential of applying models of vocal production is limited by the lack of knowledge concerning the anatomy and dynamics of vocal tracts (de Boer and Fitch 2010). "
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    ABSTRACT: The source-filter theory describes vocal production as a two-stage process involving the generation of a sound source, with its own spectral structure, which is then filtered by the resonant properties of the vocal tract. This theory has been successfully applied to the study of animal vocal signals since the 1990s. As an extension, models reproducing vocal tract resonance can be used to reproduce formant patterns and to understand the role of vocal tract filtering in nonhuman vocalizations. We studied three congeneric lemur species —Eulemur fulvus, E. macaco, E. rubriventer— using morphological measurements to build computational models of the vocal tract to estimate formants, and acoustic analysis to measure formants from natural calls. We focused on call types emitted through the nose, without apparent articulation. On the basis of anatomical measurements, we modeled the vocal tract of each species as a series of concatenated tubes, with a cross-sectional area that changed along the tract to approximate the morphology of the larynx, the nasopharyngeal cavity, the nasal chambers, and the nostrils. For each species, we calculated the resonance frequencies in 2500 randomly generated vocal tracts, in which we simulated intraspecific length and size variation. Formant location and spacing showed significant species-specific differences determined by the length of the vocal tract. We then measured formants of a set of nasal vocalizations (“grunts”) recorded from captive lemurs of the same species. We found species-specific differences in the natural calls. This is the first evidence that morphology of the vocal tract is relevant in generating filter-related acoustic cues that potentially provide receivers with information about the species of the emitter.
    International Journal of Primatology 09/2012; 33(6). DOI:10.1007/s10764-012-9635-y · 1.99 Impact Factor
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