This is a test to help identify the adaptation of the auditory system (Carhart, 1957). It involves measuring the perceptual reduction in a continuous tone over time. This can indicate towards a cochlear or neural cause ofdeafness.
The test involves looking at the patient’s response to the onset of a supra-threshold sound and then their continuous response to this as it continues over time. For example, in Meniere’s disease this is detected correctly on onset but rapidly deteriorates due to dysfunctional hair cells (Carhart, 1957). A normal response should be maintained for a minute of stimulation. Should a patient not be able to maintain this, the stimulus intensity is increased until a minute is achieved. This is only increased up to a maximum 30dB suprathreshold.
The tone decay can be run on the AC40 as standalone or by using the AC40 with Diagnostic Suite.