**2.1.3 Acoustic reflex test**

The acoustic reflex test measures the contraction of the stapedius, a tiny muscle in the middle ear, in response to loud sounds, which occurs under normal conditions when a sufficiently intense sound is presented to the auditory pathway. This muscle contraction causes a stiffening of the ossicular chain, which alters the compliance of the middle ear system. When stimulus presentation and measurement are effected on the same ear by means of the probe tone, this acoustical reflex is referred to as an ipsilateral acoustic reflex. When stimulus presentation and measurement are effected on opposite ears, the reflex is referred to as a contralateral acoustic reflex.

Stimulus tones of varying intensities of 500, 1000, 2000 or 4000 Hz are presented as short bursts. If a change in compliance greater than 0.05ml is detected, a reflex is considered to be present. Because this is an extremely small compliance change, any movement of the probe during the test may produce an artifact (false response). The test result is recorded as Pass/No Response in graphic form (MAICO, 2007). The level of loudness aids in identifying the location of the problem along the auditory pathway.
