Objective tests of the auditory system Acoustic immittance measures Static acoustic compliance Tympanometry Acoustic reflex Otoacoustic emissions (OAE) Transient-evoked OAE (TEOAE) Distortion-product OAE (DPOAE) Auditory evoked potentials Electrocochleography (ECog) Auditory brainstem response (ABR) Auditory middle latency response (AMLR) Auditory late response (ALR) 1

Acoustic reflex Contraction of stapedius muscle in response to intense sound: Results in stiffening of tympanic membrane. What to look for: Change (decrease) in tympanic membrane compliance when a signal is presented. 2

Terms related to acoustic reflex Acoustic reflex threshold (ART): Around 80 dB SL. Acoustic reflex decay: Amplitude of reflex reduces with continual stimulation. Present tone at 10 dB above ART, maintain for 10 s, check for amplitude of the reflex. Reflex decay normal at high frequencies. Significant decay at low frequencies indicates lesions of auditory nerve and brainstem. 3

Ipsilateral vs. Contralateral acoustic reflex Ipsilateral: Stimulus presented to one ear, reflex monitored in the same ear. Contralateral: Stimulus presented to one ear, reflex monitored in the opposite ear. 4

Acoustic reflex pathway 5