Chinchillas are needed as a model for understanding the physiology, development, and function of the auditory system. Their inner ear, middle ear, and Eustachian tubes are similar to that of humans, allowing advances in auditory and acoustic research. Their differences have also been important. Unlike humans, they are not susceptible to innate middle ear infections, so chinchillas have been a useful model in studying these types of infections. Other areas of research needing the chinchilla include upper respiratory tract infections, hearing, psychoacoustics, and ototoxicity.