otometrics MADSEN Midimate 622, Руководство пользователя

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7.6 FREE-FIELD SPEECH AUDIOMETRY
The MIDIMATE 622 is designed so that it can be used for free-field speech
audiometry in combination with suitable power amplifiers and loud-
speakers. Different types of amplifiers may be used depending on the
maximum intensity level required in the free field. These intensities can vary
from 80-100 dB above threshold, corresponding to 100-120 dB sound
pressure level.
Both distance from the loudspeaker to the patient and the degree of
absorption of the sound room are very critical factors. Power free-field
amplifier/loudspeaker units are specially designed to meet these
requirements.
To select speech audiometry for free field, select the following setup from the
Select Function Menu:
Speech, F.F., Left, Tape, No Mask
The following appears on the display:
-Speech- F.F. L:Tape
-Test- 20 dB
This setup selects Tape signal as input to the Left amplifier and disables the
masking channel.
Alternatively, masking may be selected-the signal may be either white noise
or speech noise or external, i.e. the masking signal may be selected from the
Tape 2 input.
Pressing L/R SHIFT interchanges the signal to the loudspeakers in the same
way as it shifts the signal between the earphones.
L/R SHIFT
The Tape 2 signal may be adjusted by pressing the Tape 2 pushbutton and
turning one of the rotary knobs simultaneously. In this case, the Stimulus
LED functions as a VU meter for the
masking signal and the sensitivity of the
Tape 2 signal may be adjusted until it deflects to zero.
When the Tape 2 pushbutton is released, the VU meter once again monitors
the stimulus signal.
Free-field speech audiometry is especially used for fitting hearing aids,
particularly for the perceptive type hearing loss where the hearing aid's
frequency response, and setting of the AVC, is of great importance in order to
obtain as good a discrimination percentage as possible (as little
discrimination loss as possible).
Free field speech audiometry is also very useful in connection with
examining children as many children dislike wearing headphones. By
examining children with narrow-band noise masking in free field, a very good
idea of their hearing ability is obtainable.
MIDIMATE 622 OPERATION MANUAL 7. Speech Audiometry
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