Otoacoustic emissions, also known as OAEs, are tiny sounds generated by movement of outer hair cells of a normal inner ear following auditory stimulus. These sounds are recordable using a probe in the ear canal. OAEs are absent when there is a mild or greater sensorineural hearing loss (more than 30dB), and absent when there is middle ear fluid. Auditory Brainstem Response Evaluation (ABR) is a type of test, usually performed for infants and young children that measures how well sounds travel along the hearing nerve pathways from the ear to the brainstem. Because OAEs measure the function of the cochlea, while ABRs measure the function of auditory nerve pathways, OAEs and ABRs can be used together to determine whether a hearing loss is sensory (cochlear) vs. neural in origin.