David G. Browning - firstname.lastname@example.org
Department of Physics
University of Rhode Island
Kingston, RI 02881
Peter M. Scheifele - email@example.com
Department of Animal Science
University of Connecticut
Storrs, CT 06209
Popular version of paper 4aAB5
Presented Thursday morning, October 20, 2005
ASA/NOISE-CON 2005 Meeting, Minneapolis, MN
In contrast to cows, sheep or goats, the equines (donkeys, horses, and zebras) can make sounds with a variable frequency content.
Of the equines, a horse appears to have the most controlled vocalization particularly during the sound most associated with it: a whinny.
When threatened a horse is a "flee-er" by nature and, gifted with excellent eyesight, is usually motivated by visual signs. However since fleeing is very energy demanding, the gathering of additional audible clues might be very beneficial.
An acoustic analysis of a typical whinny reveals two principal components; first, a constant tone with a number of harmonics which seem to increase (in bandwidth) as the animal becomes more agitated, hence we refer to it as the "emotional" component. This would generally correspond to Morton's criteria for animal vocalization.
The second component has a specific acoustic signature, that is a characteristic variation of frequency with time, which may be associated (admittedly loosely at this early stage of investigation) with a particular action such as calling or greeting.
Although the study of the nature of this component has just begun we refer to it as the "expressive" component.
The "emotional" and "expressive" components appear to be independent. so for example, a horse calling in an excited state would sound differently than normal but only because of a change in the "emotional" component, not in the "expressive" component.
Conversely, a horse answering rather than calling would sound differently because of a change in the signature of the "expressive" component, not in the "emotional" component.
We may be on the threshold of starting to quantify what experienced horse lovers may have known all along.