Welch Allyn GSI 38 - Pneumatic System and Test Timing; Acoustic Reflex Stimulus System

Pneumatic Svstem
Pressure Range (corrected for altitude): + 200 to - 400 dapa (1 dapa = 1.02 mm
water)
Pressure sweeps to at least -100 dapa if tymps complete otherwise sweeps to -400
daPa
Pressure Accuracv:
+/- 15% or +/- 10 daPa whichever is greater.
Rate of Sweep:
600 daPa/sec - for tymp slopes of <0.2 ml per 24 daPa
200 daPa/sec - for tymp slopes =,> 0.2 ml per 24 daPa
Test Time
Approximately 1 sec (high relative tymp will take longer).
Direction of Sweep:
Positive to Negative
ACOUSTIC - REFLEX ACTIVATING STIMULUS SYSTEM
Stimulus Frequencies:
500, 1000, 2000, and 4000 Hz
Stimulus Freauencv Accuracv:
+/- 3%
Stimulus Total Harmonic Distortion:
Stimulus Output Levels:
<5% measured acoustically
except at 4 khz
where speaker driving signal
is measured
IPSI: 500, 4000 Hz
80, 90, 100
dB HL
1000, 2000 Hz 85, 95, 105 dB HL
(Time multiplexed with probe tone, 106 ms On/53 ms Off Cycle)
CONTRA:
500, 1000, 2000 and 4000 HZ 90, 100, 110 db HL
(Steady tone, non multiplexed)
Equivalent Hearing Threshold Levels, in DB SPL