Interpretation l Normal acoustic reflex threshold l Elevated

Interpretation l Normal acoustic reflex threshold l Elevated acoustic reflex threshold l Lowered acoustic reflex threshold l Absent acoustic reflex

Acoustic reflex results: Patterns

Objective tests of the auditory system 1. Acoustic immittance measures l Static acoustic compliance l Tympanometry l Acoustic reflex 2. Otoacoustic emissions (OAE) l Transient-evoked OAE (TEOAE) l Distortion-product OAE (DPOAE) 3. Auditory evoked potentials l Electrocochleography (ECog) l Auditory brainstem response (ABR) l Auditory middle latency response (AMLR) l Auditory late response (ALR)

Otoacoustic emissions l Sounds generated by the cochlea and recorded in the external auditory meatus. l By-product of the active non-linear cochlea. l Conductive pathway must be normal for OAEs to be recorded. l Types: l Spontaneous (SOAE) l Evoked: Distortion-product OAE (DPOAE) Transient-evoked OAE (TEOAE)

Spontaneous OAE l l Occur in many normal ears Level: About 10 d. B TEOAE l l l Transient sounds like clicks or tone-bursts. Present many stimuli (260 to 500). Average responses to separate emissions from the noise floor. DPOAE l l l Two pure tones (f 1 and f 2) that vary in frequency. Cochlea produces additional tones called distortion products. Does not require as many stimulus repetitions and averaging as TEOAE