acoustic reflex, a paired reaction with bilateral contraction following unilateral sound exposure. The muscle contractions pull the stapes out of the oval window and thus protect the internal ear from damage caused by loud noise. The acoustic reflex threshold is the lowest level of sound that will elicit an acoustic reflex and is in the range of 85 to 90 dB hearing level in individuals with normal hearing. Acoustic reflexes are usually elevated or absent in cases of conductive or sensorineural hearing loss and present at normal or lower levels in the case of cochlear hearing loss.
