A Time Domain Acoustic Model for the Production of Rodent Ultrasonic Vocalizations

TL;DR

This paper develops a time domain acoustic model for rodent ultrasonic vocalizations, revealing the production mechanism involving jet dynamics and resonance, with implications for understanding mammalian USV production.

Contribution

It introduces a novel nonlinear time domain model for rodent USV production based on jet-resonance interactions, providing insights into the underlying physical mechanisms.

Findings

Identifies a subglottal pressure threshold for steady oscillations.

Reproduces the 22 kHz rat alarm call at realistic pressures.

Models USV production using coupled nonlinear ODEs.

Abstract

Mammalian ultrasonic vocalization (USV) has been a subject of interest for decades. This interest has mainly been driven by the intelligence of dolphins and other odontocetes. However the semantic content of odontocete USV and its mechanism of production remain poorly understood. Serendipitously however many rodent species have convergently evolved the ability to produce USVs in a similar manner. In this paper we use rodent USV as a model process to help us gain insight into the production mechanism for mammalian USV as a whole. We derive a model that describes the production of rodent USVs by considering the interaction of an unstable jet, emerging from the vocal folds, with the passive resonance modes of the upper vocal tract. Thus our model is also a solution to a special case of the jet susceptibility problem. The derived model takes the form of a set of coupled nonlinear time domain ODEs, whose solutions are controlled by biologically relevant parameters such as subglottal pressure and vocal fold radius. In our analysis of the model we find the existence of a subglottal blowing pressure threshold ($p \approx 710$ Pa), above which steady acoustic oscillations occur. Furthermore we also reproduce the $22$ kHz rat alarm call at realistic blowing pressures ($p \approx 1500$ Pa)