Ambient noise levels in audiometric test rooms used for clinical audiometry

Recently, the American National Standards Institute (ANSI) has specified (ANSI S3.1-1991) maximum permissible ambient noise levels (MPANLs) allowed in an audiometric test room that would produce negligible masking of pure tones presented down to O-dB HL for two test conditions (ears covered, ears not covered) and three test frequency ranges (125-8000 Hz, 250-8000 Hz, 500-8000 Hz). In the present study, octave band ambient noise sound pressure levels were measured in 136 audiometric test rooms used for clinical audiometry and compared with the ANSI octave band MPANLs for each test condition and frequency range. For the ears covered condition, about 50% of the rooms were in compliance (passed) with the MPANLs for the 125-8000 Hz and 250-8000 Hz range and 82% for the 500-8000 Hz range. For the ears not covered condition, only about 14% of the rooms passed for the 125-8000 Hz and 250-8000 Hz range and 37% passed for the 500-8000 Hz range. The primary cause of the low pass rate for each test condition and frequency range was attributed to low frequency (125-500 Hz) ambient noise presumably from the ventilation system.