Using earphones, establish the threshold of the test ear for the selected frequency.
Carefully instruct the patient prior to testing that a faint but steady sound will be heard and
a small jump in loudness may occasionally occur. The patient is instructed to respond each
time he is certain that the jump is heard.
Press the SISI button and the desired dB Step size.
Select Tone or FM and route the stimulus to the test ear through Channel 1 (Right or Left).
Set the intensity for Channel 1 to 20 dB above threshold. Masking noise may be routed to
the contralateral ear through Channel 2.
Press the Interrupt button for Channel 1 (and Channel 2 if masking is being used).
Familiarize the patient with responding to noticeable increments in intensity by providing
practice trials selecting each available dB step (5 dB, 2 dB or 1 dB).
Present twenty 1 dB increments with the patient responding each time an increment is
detected. After the fifth, tenth, and fifteenth presentations, the increment can be omitted or
raised to 5 dB as a check for validity of the response and to ensure against “rhythmic
condition.”
Score each correct response by pressing the Correct button and each wrong response by
pressing the Incorrect button. The SISI percent score is displayed on the status screen.
Modifications to the SISI test
Select step sizes larger than 1 dB at 20 dB SL.
Present 1 dB increments at increasingly higher sensation levels.
Vary step sizes from 1 dB to 5 dB at 20 dB SL in both ears.
Present 1 dB increments at increasingly higher sensation levels to both ears.
Grason-Stadler GSI
®
61 CLINICAL AUDIOMETER
Short-Increment Sensitivity Index (SISI)
Patients exhibiting cochlear pathology are better able to detect small increments in intensity
at low sensation levels than normally hearing subjects or subjects with pathologies located
elsewhere in the auditory system. A continuous tone is presented to the test ear at 20 dB
SL
. Every five seconds, a selected increment in intensity is introduced to the continuously
presented tone for a duration of 200 msec.
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1761-0100 Rev. B
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