Test Procedure
– Tone Decay
Carhart Tone Decay Test (1957)
Patients with retro cochlear pathology of the eighth nerve exhibit a rapid
“abnormal auditory adaption” or “temporary threshold drift” in response to a
continuous pure tone presentation.
Presentation Level
•
Establish the patient’s hearing threshold for the test ear using earphones
or insert phones using a pulsed tone.
•
Set the hearing level for the selected channel to 0 dB SL (or 20 dB SL to
present an easier listening task). The Interrupt pushbutton may be
selected or the Tone bar may be manually depressed for the duration of
the test.
Test Instructions
•
Instruct the patient to depress the hand switch as soon as a tone is heard,
and to release the hand switch only when the tone becomes inaudible.
Test Procedure
•
Select Tone Decay from the More Tests Menu.
•
Present the continuous tone at the selected hearing level.
•
When the patient responds by pressing the patient response button, the
timer will start. The timer may be manually started by pressing the Start
pushbutton of the scorer/timer.
•
When the patient releases the patient response button, the timer will
pause. If the patient pushes the response button again, the timer will
resume.
•
Record the number of seconds the tone sustains audibility.
•
If the tone becomes inaudible before the minute criteria is met, without
interrupting the tone presentation, raise the signal level in 5 dB steps
until the tone is heard for a full minute.
•
Reset the time at each increase in signal level. Continue this procedure
until the tone is heard for a full minute, or until a level of 40 dB SL is
reached.