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one to two seconds.
b.
If no response is indicated, increase the intensity by 5 dB. Present the tone again.
c.
If no response is indicated, increase the intensity by another 5 dB.
d.
If a response is indicated, this is the second time that the individual responded to the same
intensity level. Repeat the sequence of down 10 dB and up in 5 dB increments to determine
if a correct response is detected at the same intensity level. The threshold is considered to
be the minimum level at which a response has occurred two out of three times. Press the
button when this intensity level is indicated on the screen above the test frequency
to signify that the threshold level for that frequency has been reached. Note that the
appropriate symbol (
0
= right,
X
= left) appears at the correct intensity level where the
threshold was determined.
7.
Repeat this test sequence for each frequency to be tested.
8.
When the thresholds have been obtained for all the desired frequencies, select the other ear
and repeat the sequence. Note that the display changes to a new screen for storing the second
ear
’
s results. The test protocol follows a down 10 dB and up 5 dB sequence to establish
threshold level.
AUTOMATIC HEARING LEVEL
The Automated Hearing Level Procedure (Auto HL) allows the patient to control the evaluation using
the response button. The software determines the presentation level of the stimulus based on the
Hughson-Westlake Threshold estimation procedure (reference). The patient should be instructed to
hold the button down when s/he hears the tone and release the button when the tone goes off. In
this procedure, the stimulus level is decreased 10 dB each time the patient presses the button and
increased by 5 dB when the button is not pressed. The GSI 39 will present the stimulus and increase
or decrease the intensity of the stimulus based on the patient response. The GSI 39 monitors the
response/no response stimuli and determines the hearing threshold based on the data.
Theory of Operation
The following bullet points describe the stimulus presentation patterns and patient response validity
1.
The stimulus on-time is fixed at 1.5 seconds.
2.
The Inter-stimulus interval is randomized between 3 and 5 seconds.
3.
When a valid response occurs, the intensity for the next stimulus presentation is decreased
10 dB. When no valid response occurs, the intensity of the next stimulus presentation is
increased 5 dB. This is based on the Hughson-Westlake down 10, up 5 dB rule used by most
audiologists during threshold testing.
4.
The system will determine the response to be valid if the patient response switch is pressed
during the stimulus or for 2 seconds following the stimulus off time.
5.
The system will determine the patient response to be invalid based on the following
occurrences:
a.
The patient response switch is pressed during the stimulus on time, but not released before