While the human’s frequency range of audibility has been well documented at 20–20 000 Hz, the audible frequency ranges vary considerably from species to species. As such, that which constitutes the “high-frequency” range is quite different in mice, rats, guinea pigs, gerbils, chinchillas, and cats. These mammalian species have been frequently used in anatomical and physiological investigations of the peripheral and central auditory nervous systems. Much of what we know about the physiology of the auditory system is based upon on these animal species, yet many of their auditory systems operate in a much different frequency range from the human’s. We will discuss the use of auditory electrophysiology to define the high-frequency ranges across several different mammal species, and then transition to a comparison of their high-frequency ranges to that of the human. Further, we will discuss the implications of trying to extrapolate insight into human auditory physiology from animal species whose high-frequency ranges are quite different from our own.