Nonlinear Dynamics and Temporal Analysis
Pp. 336-357 (22)
Isao T. Tokuda
Animal vocalizations range from tonal sounds produced by almost periodic
vocal fold vibrations to completely aperiodic sounds generating noisy signals. Between
these two extremes, a variety of nonlinear phenomena such as limit cycles,
subharmonics, biphonation, chaos, and bifurcations have been found. This chapter
introduces a concept of nonlinear dynamics and its methodology applicable to
bioacoustic data. Since conventional spectral analysis is not sufficient to characterize
nonlinear properties of the recorded sound signals, a temporal analysis based upon the
method of nonlinear dynamics is developed. First, using a mathematical model of the
vocal folds, basics of nonlinear dynamics and bifurcations are illustrated. The temporal
analysis is then applied to acoustic data from real animal vocalizations. Our focus is on
extracting low-dimensional nonlinear dynamics from several samples of vocalizations
ranging from tonal sounds to irregular atonal sounds. We demonstrate that nonlinear
analysis is a profitable approach for analyzing mammalian vocalizations with a
harmonic composition or low-dimensional chaos.
Animal vocalization, Chaos, Data analysis, Nonlinear dynamics.
Department of Mechanical Engineering, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga 525-8577, Japan.