Tone decay test

The tone decay test (also known as the threshold tone decay test or TTDT) is used in audiology to detect and measure auditory fatigue. It was developed by Raymond Carhart in 1957. In people with normal hearing, a tone whose intensity is only slightly above their absolute threshold of hearing can be heard continuously for 60 seconds. The tone decay test produces a measure of the "decibels of decay", i.e. the number of decibels above the patient's absolute threshold of hearing that are required for the tone to be heard for 60 seconds. A decay of between 15 and 20 decibels is indicative of cochlear hearing loss. A decay of more than 25 decibels is indicative of damage to the vestibulocochlear nerve.