Amplitude and frequency modulation control of sound production in a mechanical model of the avian syrinx

Abstract

SUMMARYBirdsong has developed into one of the important models for motor control of learned behaviour and shows many parallels with speech acquisition in humans. However, there are several experimental limitations to studying the vocal organ -the syrinx -in vivo. The multidisciplinary approach of combining experimental data and mathematical modelling has greatly improved the understanding of neural control and peripheral motor dynamics of sound generation in birds. Here, we present a simple mechanical model of the syrinx that facilitates detailed study of vibrations and sound production. Our model resembles the 'starling resistor', a collapsible tube model, and consists of a tube with a single membrane in its casing, suspended in an external pressure chamber and driven by various pressure patterns. With this design, we can separately control 'bronchial' pressure and tension in the oscillating membrane and generate a wide variety of 'syllables' with simple sweeps of the control parameters. We show that the membrane exhibits high frequency, self-sustained oscillations in the audio range (>600 Hz fundamental frequency) using laser Doppler vibrometry, and systematically explore the conditions for sound production of the model in its control space. The fundamental frequency of the sound increases with tension in three membranes with different stiffness and mass. The lowerbound fundamental frequency increases with membrane mass. The membrane vibrations are strongly coupled to the resonance properties of the distal tube, most likely because of its reflective properties to sound waves. Our model is a gross simplification of the complex morphology found in birds, and more closely resembles mathematical models of the syrinx. Our results confirm several assumptions underlying existing mathematical models in a complex geometry.

The vocal repertoire of the domesticated zebra finch: a data-driven approach to decipher the information-bearing acoustic features of communication signals

“…Vocalization types vary in their pitch saliency from the very noisy aggressive ( Wsst call) and Distress calls to the very tonal contact calls ( Distance calls, Tet calls and Long Tonal calls). The pitch is produced by the birds’ vocal organ, the syrinx (Fee, 2002; Goller and Larsen, 1997), and models suggest that noisy sounds could also be generated at the syrinx when high air-sac pressure drives the system into chaotic regimes (Elemans et al, 2009; Fee et al, 1998). Thus, control of the syrinx in conjunction with the respiratory system will be key for controlling the pitch (the fundamental), the pitch saliency, the duration and the amplitude of the sounds.…”

The songbird syrinx morphome: a three-dimensional, high-resolution, interactive morphological map of the zebra finch vocal organ

“…Gaunt previously proposed that more elaborate intrinsic muscles in songbirds allowed for independent control of song parameters [20]. Field recordings [91], excised preparations [92], mechanical models [93,94] and numerical models of sound production in non-songbirds, such as ringdoves ( Streptopelia risoria ) [95], and sub-oscines (Passeriformes: Tyranni), such as the great kiskadee ( Pitangus sulphuratus ) [96], show that sound amplitude and frequency are often coupled to some degree, thereby severely limiting the potential repertoire of syllables that can be produced physically. To our knowledge, none of these species appears to have evolved a structure comparable to the MVC found in the songbird syrinx that could allow for tension control without affecting position.…”

Sloshing and slamming oscillations in a collapsible channel flow

“…Under certain conditions, the internal flow can be strongly coupled to deformation of the vessel, giving rise to nonlinear flow resistance properties (such as flow limitation in forced expiration) and instabilities manifested as Korotkoff noises during sphygmomanometry and various respiratory sounds (wheezing from bronchial airways, snoring from the pharynx, vocalization from the larynx and birdsong from the syrinx) (see Grotberg & Jensen 2004;Thomson, Mongeau & Frankel 2005;Bertram 2008;Elemans et al 2009;Dempsey et al 2010). These applications raise some fundamental questions in fluid-structure interaction, such as: what are the mechanisms that drive instabilities; how, and to what extent, are instabilities in a compliant vessel coupled to distant regions of the flow domain; and what factors might regulate transient opposite-wall contact during an oscillation (e.g.…”