The vast majority of hearing tests carried out as routine procedures are based on the willingness and ability of the patient to report his hearing sensations. Realizing the disadvantages of subjective audiometry, it is not surprising that numerous attempts have been made to find a criterion by which the function of the hearing organ is determined by observations which are independent from statements of the patient. A definition of terms is essential. We are concerned with objective quantitative measurements of the function of the cochlea in perceiving sound. The term 'hearing" as connotating a cortical function is avoided, and emphasis is placed on the cochlear function. Sound perception and cochlear function are used here as synonyms. Objective audiometry is defined as the determination of sound perception which is not based on the sensations or descriptions of the examined person. This discussion deals with an unconditioned muscle reflex which is produced