Maico MA 42, Руководство по эксплуатации

Страница: 18 / 64

Operating Instructions MA 42
Operating_Instructions_8100460-6_MA42_e_15a
16
8100460-6 1/15
Automatic masking:
With the manual masking, as described before, you have to readjust the
masking level every time you change the test signal level. The MA 42 has a
tracking feature for easy masking.
Adjust the test signal using the level control dial and with the opposite level
control dial the corresponding masking level.
Now press the TRACK button. The masking level is automatically changed if
you adjust the test signal level (e.g. if the test level was 30 dB
HL
and the masking
level 50 dB
HL
and you change the test level to 45 dB
HL
the masking level is
automatically adjusted to 65 dB
HL
).
5.1.2 High tone audiometry (optional)
If available, pure tone hearing threshold of high frequencies from 8 kHz to 20
kHz can be tested. The High Tone option need to be activated and the
transducer HDA300 need to be calibrated for all frequencies.
First select the corresponding output Phones or Insert by the button (10) or (16).
The item High Tone is now available at the functional button (17). Select High
Tone by pressing the functional button (17) till High Tone is highlighted. The
high tone diagram is displayed, combining the left and right ears results.
Additional frequencies from 8 kHz to 20 kHz can be selected now by the
frequency up (4) or down (5) key. The test procedure is identical to the
description in chapter 5.1.1 Pure-tone Testing.
If a transducer is selected which is not calibrated for high frequencies, the
diagram will be set to the initial diagram settings and the high frequencies can’t
be selected anymore.
On the printout, pure tone audiometry results will appear in a high tone
diagram combining left and right ears results.
5.1.2 Bone conduction testing
Bone conduction - the transmission of sound waves through the skull directly
to the inner ear - provides information about the function of the inner ear. For
a neural hearing loss the values of air conduction and bone conduction are the
same. In this case a hearing loss of the middle ear can be eliminated.
Place the bone conduction receiver so that the flat, circular side of the
transducer is placed on the mastoid, at the noticeable ledge of the cranial bone
behind the auricle. The other side of the headband is placed in front of the
opposite ear.
Set the receiver selector to Bone and the signal selector to TONE.
Perform the test the same way as for air conduction.