From anatomy to acoustics, a study of the sound generation process in baleen whales (mysticetes)

Abstract

The mechanism of baleen whale (mysticete) sound production is a topic of much interest, particularly as they make the loudest natural sounds and transmit them across the longest distances. Prior studies on mysticete sound generation have explored either acoustics or anatomy, but unfortunately have done so in isolation of the other discipline. This study links the two disciplines to derive a comprehensive understanding of the sound production process. Anatomical data (vocal fold measures, respiratory tract volumes, air flow paths) are used to derive initially an acoustic model that explains how sounds are made and transmitted. The model is then tested by comparisons to parameters (frequency, amplitude, duration) derived from hydrophone recordings of live whales. The model defines four mutually exclusive components: air sources (providing initial energy), vibrators generating harmonic frequencies (vocal folds, corniculate flaps), air flow paths (between lungs, trachea, laryngeal sac, nasal cavities), and radiating areas (transmitting sound energy to water). This model explains, for the first time, the acoustic function of each part of the mysticete sound generating system.Grant Funding Source: AAA