7.4.2 RECORDED WORD LISTS (DISCRIMINATION TEST)
Select the following setup:
Speech, Air, Left, Tape, No Mask.
The following display appears:
-Speech- Air
L:Tape
-Test-
20 dB
Start playback unit and make sure the VU meter gives deflection to O VU. If
necessary, adjust Tape 1 level by pressing Tape 1 to display the VU meter
and then turning one of the rotary knobs. The HTL level can then be read
directly on display.
For this test use word lists with phonetically balanced words. Each ear is
tested in turn and the patient is asked to repeat the words he hears. The
intensity is normally set at a level of 40 dB above the patient's threshold.
Patients with normal hearing will be able to repeat 100% of the presented
words. In some cases of hearing loss, the discrimination is only 40-50% or
less, independent of intensity. There are cases where increase in intensity
above a certain level gives a poorer discrimination.
7.5 SPEECH AUDIOMETRY AND MASKING
Masking is very important in speech audiometry as there is still the risk of
response from the ear not being tested. In word discrimination testing, this
danger is greater than in pure tone audiometry since the signal is presented
to the test ear at a suprathreshold level. “Masking must be used whenever
the presentation level for this suprathreshold task, minus the interaural
attenuation, exceeds the bone conduction thresholds of the nontest ear”
(Jean H. Lovrinic, in Audiology for the Physician, 1980).
Speech noise is generally recommended as the masking noise of choice but
white noise is also favored by many-narrow-band noise, while used
extensively in pure tone audiometry, is too narrow in frequency response for
use in speech audiometry. Speech noise is actually white noise filtered to a
low and middle frequency spectrum.
For speech audiometry, the Midimate 622 enables masking to be employed
together with Air, Bone and F.F. outputs. Contralateral, ipsilateral and
binaural routings are available just as in pure tone audiometry, and white
noise, speech noise or external (Ext) may be selected. The External choice
enables any type of prerecorded masking to be used via the Tape/CD input.
To select masking for speech audiometry, select the following setup from the
Select Function Menu:
Speech, Air, Left, Micr., Air.
The following appears on the display:
MIDIMATE 622 OPERATION MANUAL
7. Speech Audiometry
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