• If a walk-around sound survey indicates excessive noise levels, employers will need to implement additional monitoring.

When the results of the walk-around survey indicate that noise levels may exceed those outlined in the Occupational Safety and Health Administration (OSHA)’s Occupational Noise Exposure standard at 1910.95, additional monitoring is necessary. Sample the noise exposures of representative employees from each job classification that may be potentially overexposed.

Use a dosimeter with a threshold of 80 decibels (A-weighted sound pressure level) and 90 decibels to measure noise exposures. Most modern dosimeters use simultaneous 80 and 90 decibel thresholds.

• A dosimeter with a threshold of 80 decibels is used to measure the noise dose of those employees identified during the walk-around survey as having noise exposures that are in compliance with Table G-16 of OSHA’s noise standard 1910.95, but whose exposure may exceed the levels specified in Table G-16a [1910.95 Appendix A: Noise Exposure Computation]. In other words, the 80-decibels threshold is used to determine compliance with the 85 decibels time-weighted average (TWA) action level under OSHA’s noise standard.
• The dosimeter with a threshold of 90 decibels is used to measure the noise dose of those employees identified during the walk-around survey as having potential noise exposures that exceed the sound levels in Table G-16. In other words, the 90 decibels threshold is used to determine compliance with the permissible exposure limit (PEL).

As a minimum, sampling should be conducted for a length of time necessary to establish whether exposures are above the limits permitted by Table G-16 or Table G-16a. Instrument accuracy must be taken into account. Employers should consider the following with respect to the monitoring results:

• TWA exposures at or above the action level of 85 decibels require a hearing conservation program (results obtained from the 80 decibels threshold).
• TWA exposures exceeding the PEL (Table G-16) require feasible engineering or administrative controls to be implemented (results obtained from the 90 decibels threshold).