All Audiology Instruments for testing hearing are manufactured to a ANSI ( American National Standards Institute) standard for hearing test instruments, There are also standards for spirometry and vision test equipment.
ANSI S3.1-1991
ANSI S3.1- 1999 (Rev. 2008)
For ambient noise levels for hearing test enclosures for diagnostic test facilities.
OSHA
ANSI S3.6-1969 for Audiometers ** see note below
Ambient noise levels for test room environments for Hearing conservation programs per Subchapter 7. General Industry Safety Orders,Group 15. Occupational Noise, Article 105. Control of Noise Exposure