GSi 61 - Page 42

Grason-Stadler GSI
®
61 CLINICAL AUDIOMETER
Initial Installation
Elimination of Ambient Noise
The GSI 61 can be installed in a single room environment or as part of a two room
suite
.
Excessive noise in the test environment, such as that produced by conversation,
typewriters, printers, or other machines reduces test validity because it tends to
mask the test signals, particularly at the lower frequencies where earphone cushions
provide less effective attenuation. A room that attenuates sound may be required if
ambient noise at the patient’s ears reaches levels sufficient to cause apparent hearing
loss at the lower frequencies.
Maximum permissible test environment sound-pressure levels are specified by
American National Standard Criteria for Permissible Background Noise during
Audiometric Testing, Section 3.1. The following table shows the maximum background
levels that can be present inside the room while a valid hearing test is being conducted.
These values apply for hearing threshold measurements to 0 dB HL.
Maximum Ambient Noise
Test
Tone
Freq.
(Hz) 125 250 500 750 1000 1500 2000 3000 4000 6000 8000
Test
Room
level
max
dB SPL,
ears
covered 29.0 17.5 14.5 16.5 21.5 21.5 23.0 28.5 29.5 33.0 38.5
Max
level dB
SPL,
ears not
covered 23.0 13.5 9.5 7.5 9.0 5.5 3.5 3.5 4.0 9.0 15.5
Notes:
Maximum permissible 1/3 octave band level
If the Hearing Level to be measured is -10 dB HL, then 10 dB should be subtracted from the levels
listed in this table.
Note: A room providing sound isolation from ambient noise is highly recommended
so that hearing threshold values may be obtained. If a separate examination (sound)
room is used, it is considered sufficiently quiet for the purposes of these tests if a
group of otologically “normal” listeners with their ears occluded is unable to detect
any ambient noise during the test period. See ANSI S3.1 Criteria for Permissible
Ambient Noise during Audiometric Testing for maximum allowable outside octave
band noise levels with three prefabricated sound room types.
Note: Live voice testing requires a separate sound attenuated room for the patient in
order to avoid feedback and direct transmission of the test stimuli.
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