Acoustic signatures of sound source-tract coupling

EZEQUIEL M. ARNEODO; YONATAN SANZ PERL; GABRIEL B. MINDLIN

PHYSICAL REVIEW E

AMER PHYSICAL SOC

Año: 2011 vol. 83 p. 419201 - 419209

1539-3755

   Birdsong is a complex behavior, which results from the interaction between a nervous system and abiomechanical peripheral device. While much has been learned about how complex sounds are generated inthe vocal organ, little has been learned about the signature on the vocalizations of the nonlinear effects introducedby the acoustic interactions between a sound source and the vocal tract. The variety of morphologies amongbird species makes birdsong a most suitable model to study phenomena associated to the production of complexvocalizations. Inspired by the sound production mechanisms of songbirds, in this work we study a mathematicalmodel of a vocal organ, in which a simple sound source interacts with a tract, leading to a delay differentialequation. We explore the system numerically, and by taking it to the weakly nonlinear limit, we are able to examineits periodic solutions analytically. By these means we are able to explore the dynamics of oscillatory solutions ofa sound source-tract coupled system, which are qualitatively different from those of a sound source-filter modelof a vocal organ. Nonlinear features of the solutions are proposed as the underlying mechanisms of observedphenomena in birdsong, such as unilaterally produced “frequency jumps,” enhancement of resonances, and theshift of the fundamental frequency observed in heliox experiments.