Before commencing the test, adjust Microphone Level. Put on the monitor
headset or place the microphone approximately 20 cm from your mouth, and
read from the word list. At the same time adjust Microphone Level so that
channel 1 VU meter gives peak deflection to 0 VU. The Microphone Level is
adjusted by pressing the microphone pushbutton to display the VU meter and
simultaneously turning one of the rotary knobs. The intensity of the speech
presented to the patient can now be read on the stimulus LED. The intensities
shown are dB re normal threshold. During the test the operator should speak
with the same intensity and keep the same distance from the microphone in
order to maintain deflections on the VU meter at zero.
Use a word list intended for threshold measurements. Test each ear in turn
(use the L/R Shift pushbutton) and ask the patient to repeat the words he
hears. Set stimulus Hearing Level so that the patient can just repeat the
words with certainty. Then reduce intensity in 5 dB steps using Hearing Level
until the patient can only repeat 50% of the presented words. Then read the
hearing loss on the digital read out. In order to assure as valid a
measurement as possible, 20 words should be presented to the patient.
Under normal conditions the threshold can be found by using a few words
and the rest are only used to confirm the test.
7.3.2 LIVE VOICE DISCRIMINATION TEST
Select the following setup:
Speech, Air, Left, Micr., No Mask.
This results in the following display:
-Speech- Air
L:Micr
-Test-
20 dB
Before commencing the test, adjust Microphone Level. Put on the monitor
headset or place the microphone approximately 20 cm from your mouth, and
read from the word list. At the same time adjust Microphone Level so that
channel 1 VU meter gives peak deflection to 0 VU. The Microphone Level is
adjusted by pressing the microphone pushbutton to display the VU meter
and then turning one of the rotary knobs. The intensity of the speech
presented to the patient can now be read on the stimulus LED. The
intensities shown are dB re normal threshold. During the test the operator
should speak with the same intensity and keep the same distance from the
microphone in order to maintain deflections on VU meter at zero.
Adjust
Microphone Level
For this test, use word lists with phonetically balanced words. Each ear is
tested in turn (use the L/R Shift pushbutton) 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.
MIDIMATE 622 OPERATION MANUAL
7. Speech Audiometry
43
