Equipment for measuring OAE Depends on the type of OAE. For SOAE: Probe with tiny sensitive microphone For TEOAE: Probe with miniature loudspeaker to present the click or tone burst, and a microphone to pick up emissions For DPOAE: Probe containing two loudspeakers and a microphone 1

OAE Diagnostic value Very useful in difficult-to-test populations. If emissions are present: Conductive pathway is normal. The particular region of the cochlea is normal. If emissions are present in case of SN hearing loss: Problem not in OHC, but in regions beyond the cochlea (retrocochlear) If emissions are absent in case of SN hearing loss: Problem in cochlea (OHC), but could also be retrocochlear problems. 2

Auditory evoked potentials Electrical responses that occur in the cochlea and auditory pathways in response to sound. Measured by presenting a series of sounds through transducers. Responses picked up by electrodes placed at various locations. Responses averaged to remove noise. Terms: Latency: Time between introduction of stimulus and the occurrence of the response. Depends on the part of the auditory system that generates the response. Amplitude: The strength of the measured response. 3

ABR Early responses (10-15 ms latency). Originate from the eighth nerve and brainstem. Present a series of clicks or tone-bursts. Measure responses in a graphical form (waveform). Each part of the waveform thought to arise from a specific part of the auditory pathway. 4

Probable sites of origin (Møller, 1985) Wave number Site of generation I VIIIth nerve II III Pons IV V Midbrain VI and VII ?? 5

Normal ABR 6