Bioacoustics is the study of sound in animals and includes, but is not limited to, animal communication with associated behavior, sound production anatomy and neurophysiology, auditory capacities and auditory mechanisms, and animal welfare. The present research investigates the vocalizations of horses during stressful situations. Stress can be positive or negative. Distress is anything that affects the animal in a negative way, such as in mare and foal separation. Eustress is anything that affects the animal in a positive way, such as morning feeding time in a horse barn. The purpose of the current research is to find spectral differences in the recorded vocalizations of stalled horses that indicate both distress and eustress using the Hidden Markov Model (HMM). Greenwood Function Cepstral Coefficient values suggest that there are spectral differences between vocalizations in a distress and eustress situation. These consistent results indicate that further research to obtain and evaluate vocalizations of horses may provide a productive tool in understanding equine welfare.
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