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Instruction
Instructionmanual
manual
62
62
Chapter 1: Instructions for Installation and Use
Although experience largely dictates the process and level of
noise to apply, a recommended method for determining hearing
thresholds with masking is presented below.
1
Apply a test tone to the ear being tested with a level equal
to the hearing threshold without masking. Select narrow band
noise NBN in the other audiometer channel and apply a level of
effective masking to the other ear that is equal to the hearing
threshold level of the latter.
Increase the level of masking until the test zone is inaudible
or until it exceeds the level of the test tone.
2 If the test tone is still audible when the level of noise is
equal to the level of the tone, this is taken as the hearing
threshold. If the test tone remains masked, the level of the
latter is increased until it is audible once again.
3 Increment the noise level in 5 dB steps. If the test tone
is inaudible, increase the level until it is audible once again.
Repeat this process until the test tone remains audible even
though the level of masking noise has been increased by more
than 10 dB. This level of masking (which is the level from which
no subsequent increase in the level of tone was required to
make it audible) is the correct level and this process should
have resulted in the correct hearing threshold for the test
frequency. Make a note of the correct level of masking.
DETERMINATION OF THE HEARING THRESHOLD VIA BONE
CONDUCTION WITHOUT MASKING
The SIBELSOUND 400 audiometer provides the following
frequencies and pure tone levels for application by bone
conduction:
Hz
250
500
750
1000
1500
2000
3000
4000
Máx dB HL
50
60
60
70
70
70
70
70
Mín. dB HL
-10
-10
-10
-10
-10
-10
-10
-10