Welch Allyn AM 232 Manual Audiometer - User Manual - Manual (Page 15)

15 12-16-08
Pretest procedure
Note: The AM 232 is a versatile audiometer designed for use in doctor offices,
schools, industrial settings, the military, etc. The generic term “subject” used in this
manual is used to identify the person whose hearing is being evaluated.
Any program aimed at obtaining reliable records of hearing thresholds should be
staffed and supervised by appropriately-trained individuals. Training courses
leading to certification are available for audiometric technicians in most urban areas.
Two prerequisites are of particular importance to the procurement of reliable audio-
grams:
•
Prior to testing, allow adequate time for the subject to recover from the effects of
a previous exposure to high-level sound.
• Tests should be performed in a quiet area.
Pretest noise recovery period
Exposure to high levels of sound (unmuffled lawn mowers, power tools, loud music,
gunfire, etc.) tends to create a temporary threshold shift (TTS), which diminishes with
time after exposure. Any subject tested soon after such exposure may manifest a
hearing loss that does not reflect the subject’s normal hearing threshold. It is,
therefore, important that the testing procedure prescribe some time interval - usually
at least 16 hours - between the last exposure to high-level sound and the administra-
tion of any hearing test.