Free-Field Thresholds - otometrics Madsen Midimate 602 Quick Manual

MIDIMATE 602 & 622 Diagnostic Audiometers
other. This is to avoid "false" contralateral masking caused by the high masking level
required in the weaker ear.
The test procedure is similar to that described in §4.2.1.
4.3

Free-Field thresholds

Free-field pure-tone testing, with loudspeakers instead of headphones, is used pri-
marily when the patient for instance is a child who dislikes wearing headphones.
However, the measured thresholds will be influenced by:
•
The distance from the loudspeakers to the patient;
•
The acoustic absorption of the walls of the test room;
•
Ambient noise.
Loudspeakers (such as 8–02–450) and a two-channel power amplifier such as PA 210 (8–02–
240) for free-field testing are optional accessories.
To set up a free-field tone test, do as follows:
1. Connect the amplifier's left and right inputs to FF, L and R on the rear panel.
2. Connect the loudspeakers to the amplifier's outputs.
3. Press Menu to display the Select Function menu.
4. From the Select Function menu press Softkey 1 to select the (Tone) Out-
put ? menu.
5. From the (Tone)Output ? menu press Softkey 3 to select F.F.
6. From the (Tone,F.F) Side ? menu press Softkey 1 to select Left.
7. From the (Tone,F.F,Left) Masking ? menu press Softkey 3 to select FF.
To minimize the influence of standing waves on the measured threshold, the test
tone is frequency modulated to a depth of ±5% by a warble tone. If required, you can
disable this by toggling Softkey 2 so that C/P/W is displayed instead of C/P/W.
To use the narrow band noise provided for masking as an alternative test source in-
stead of tone, do as above but with the following differences:
8. Press Softkey 2 to select Right instead of Left in step 5.
9. Toggle Softkey 4 to display F.F On/Off.
10. Turn the Hearing Level wheel counterclockwise to reduce the tone to minimum.
11. Use the Masking Level wheel to see the threshold (displayed above Softkey 5)
for each center frequency.
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