beautypg.com

Elimination of ambient noise, Permissible noise levels – Welch Allyn AM 232 Manual Audiometer - User Manual User Manual

Page 16

background image

16

12-16-08

Elimination of ambient noise

Excessive noise in the test environment such as that produced by conversation,
typewriters, or other machines also reduces test validity because it tends to mask the
test signals particularly at the lower frequencies where earphone cushions provide
less effective attenuation. An acoustically tested room may be required if ambient
noise at the subject’s ears reaches objectionable levels - i.e., sufficient to cause
apparent hearing loss at the low frequencies. Also, Audiocups are available from
Welch Allyn as an optional accessory. If the test subject is in the same room as the
audiometer, it is recommended that the subject be seated about 1 meter (-3 ft) away
from the instrument.

Maximum permissible test environment sound-pressure levels are specified by
American National Standard Criteria for Permissible Background Noise during
Audiometric Testing, S3.1-1977 (revised). Table 2 shows the maximum background
levels that can be present inside the room while a valid hearing test is being con-
ducted. For more comprehensive information about hearing testing and hearing
conservation, refer to the Bibliography.

Permissible noise levels

Test Tone Frequency (Hz)

125

250

500

750

1000

1500

2000

3000

4000

6000

8000

Test Room

*

34.0

22.5

19.5

21.5

26.5

26.5

28.0

33.5

34.5

38.0

43.5

Test Room

**

29.0

17.5

14.5

16.5

21.5

21.5

23.0

28.5

29.5

33.0

38.5

*

Ears covered maximum permissible octave band levels.

**

Ears covered maximum permissible one-third octave band levels.