Journal of Zoology
© The Zoological Society of London
Edited By: Nigel Bennett (Editor-in-Chief), Matt Hayward, Andrew Kitchener, Mark-Oliver Roedel, Jean-Nicolas Volff, Gabriele Uhl. Reviews Editor: Trish Fleming
Impact Factor: 1.883
ISI Journal Citation Reports © Ranking: 2014: 37/154 (Zoology)
Online ISSN: 1469-7998
Sound production mechanisms in animals Virtual Issue
The modes of production of sounds and the structures used in sound production in animals are very diverse, and range from vibration of the wings in fruit flies (Drosophila) to stridulation in crickets, snapping of the swimbladder in fish, tongue clicks in some bats and vibration of the tympaniform membranes in birds or of the vocal cords in mammals. Several seminal papers on the modes of acoustic sound production and its link with the acoustic structure of vocalisations, as well as on the information content of vocalisations, have been published in Journal of Zoology. This Virtual Issue gathers a selection of reviews and research papers, from various years, on the topic of sound production mechanisms.
In the first paper, Parmentier et al. (2008) compared the structures involved in acoustic communication in three species of pearlfish (Carapidae; Carapus boraborensis, Encheliophis gracilis and Carapus homei). The authors analysed the sound production system as well as the acoustic features of the sounds produced. They were able to relate each part of the sounds to the action of swimbladder muscles of the producer. They also show anatomical as well as acoustic differences between the three studied species.
With the second and third papers selected for this Virtual Issue, we move on to bird sound production. Thorpe (1958) and Warner (1972) are among the earliest detailed accounts on the topic of sound production mechanism in birds. Thorpe (1958) is a review paper describing the vocal apparatus of birds and comparing it with human vocal apparatus. Warner (1972) is a research paper comparing the anatomy of the syrinx in several passerine birds (songbirds). Warner’s main finding is that the only demonstrable vibratile areas, hence the only sound sources, in the syrinx are the internal tympaniform membranes. These findings would be later confirmed by many other studies.
Most bats produce echolocation signals, ranging from 20 to 200 kilohertz in frequency, using their larynx. However, some variation exists. For instance, a few species click their tongue, whereas horseshoe and leaf-nosed bats emit their echolocation calls through their nostrils, which are surrounded by a fleshy, horseshoe/leaf-like structure. In the fourth paper of this Virtual Issue, Robinson (1996) investigated the function of the noseleaf of horseshoe and leaf-nosed bats in echolocation. His results show that noseleaf width is determined by wavelength rather than body size, thus highlighting the importance of the noseleaf in shaping the echolocation signal.
The next paper selected for this Virtual Issue, Frazer Sissom et al. (1991), investigates purring in cats. The mechanisms of cat purring have turned out to be challenging to understand. Indeed, the very low fundamental frequency of purring, notably in domestic cats (around 25 Hertz), suggests alternative mechanisms of sound production than flow-induced vocal cord vibration, as only very long cords could produce such low frequency. The authors recorded domestic cats in a shelter. Their results suggest that purring could arise from the gating of respiratory flow by the larynx. This had been suggested also by Remmers and Gautier (1972), who showed that purring is in fact produced by active contractions of laryngeal muscles modulating the respiratory air flow passing through the vocal cords, as opposed to flow-induced self-sustaining oscillations found, for example, in humans.
According to the source-filter theory of voice production (Fant, 1960; Titze, 1994), the air flow coming from the lungs induces the oscillation of the vocal cords, thus producing the “source” sound. This sound is then filtered in the vocal tract (“filter”). Some frequencies, which correspond to the resonances of the vocal tract, will be amplified and other frequencies will be dampened. The source determines the lowest frequency of the voice (fundamental frequency) and its harmonics, while the filter determines the spectral peaks, called “formants”. The source-filter theory framework has been recently adapted to other animals. The sixth paper of this Virtual Issue, Taylor and Reby (2010), describes how mammal communication research can benefit from this framework by highlighting information, in vocalisations, about the sender’s characteristics. The seventh paper of the Virtual Issue, Briefer (2012), describes how this framework can help to find vocal correlates of emotional arousal and valence in mammals.
The eighth paper selected for this Virtual Issue, Fitch (1999), shows how the source-filter theory framework can be applied to birds, in order to explain the evolution of trachea elongation. More than 60 bird species possess an elongated trachea. Fitch suggests that this characteristic evolved through sexual selection to exaggerate perceived body size, as animals can produce vocalisations with lower formants than expected based on their body size.
The ninth paper in this Virtual Issue investigated the source of vocal production in muskoxen (Ovibos moschatus). Although highly sexually dimorphic (males are 1/3 heavier than females), both sexes of this species produce very low roars. Frey et al. (2005) found that roars in both sexes are characterised by a pulsed structure, with a pulse rate of 20 Hz on average. The larynx size of adult male and female are remarkably similar (i.e. almost identical larynx size and vocal cord length). Muskoxen thus differ from other species with similar mating systems (e.g. fallow deer, red deer, elephant seals), in which strong sexual dimorphism is accompanied by distinct acoustic differences.
The two last papers selected for this Virtual Issue on sound production mechanisms investigated the link between vocal tract length and formant frequencies in canids (Plotsky et al. 2013) and fallow deer (McElligott et al. 2006), respectively. Plotsky et al. (2013) present one of the first clear evidence that formants provide honest vocal cues about signaller size, by testing the link between vocal tract length and measures of body size in Portuguese water dogs (Canis lupus familiaris) and Russian silver foxes (Vulpes vulpes). McElligott et al. (2006) investigated the link between vocal tract elongation and formant frequencies in fallow deer (Dama dama). This species possess a mobile larynx that can be retracted during vocalizations. The authors show that fallow buck individuals can increase their vocal tract length on average by 52% during vocalization. This phenomenon could be used by males to exaggerate their perceived body size.
We hope that you will enjoy reading this collection of papers on various modes of sound production and adaptions.
Institute of Agricultural Sciences, ETH Zürich, Universitätstrasse 2, 8092 Zürich, Switzerland
Fant, G. (1960) Acoustic theory of speech production. The Hague: Mouton.
Remmers, J.E. and H. Gautier (1972) Neural and Mechanical Mechanisms of Feline Purring. Respiration Physiology,16, 351-361.
Titze, I.R. (1994) Principles of vocal production. Englewood Cliffs: Prentice-Hall.
E. Parmentier, J.-P. Lagardère, Y. Chancerelle, D. Dufrane and I. Eeckhaut
W. H. Thorpe
Robert W. Warner
Mark F. Robinson
Dawn E. Frazer Sissom, D. A. Rice and G. Peters
A. M. Taylor and D. Reby
E. F. Briefer
W. T. Fitch
R. Frey, A. Gebler and G. Fritsch
K. Plotsky, D. Rendall, T. Riede and K. Chase
A. G. McElligott, M. Birrer and E. Vannoni