NYC-WTC_000234638

NYC 9/11 Public Portal Document

n Industrial Hygiene Noise Measurement Results Key to Noise Measurement Terminology

The following explanations should help in reading the data chart.

1. Dose (8) - Refers to the noise dose for an eight hour shift based upon the average sound pressure level measured during the noise integration time period.

2. Lavg - Refers to the average sound pressure level (dBA) the worker was exposed to during the measurement time period.

3. TWA (8) - Refers to the eight hour time-weighted average noise exposure, based upon the shift length indicated. A twelve hour shift length is assumed unless otherwise indicated by the employee.

4. Time > 115 dBA - This indicates the duration of time the worker’s noise exposure was above 115 dBA during the sample period.

5. Occupational Exposure Limits - OSHA 1910.95 • OSHA PEL or ACGIH TLV - This refers to the Occupational exposure limit to which the result should be compared. OSHA establishes Permissible Exposure Limits (PELs) that have the force of law, through a mle-making process. The OSHA Permissible Exposure Limit for noise is 90 dBA for an eight hour TWA noise exposure. • Exposures >90 dBA for an eight hour TWA require inclusion in a hearing conservation program, mandatory use of hearing protective devices. Investigation of noise reduction techniques are warranted. Exposures should also not exceed 115 dBA for > 30 seconds/day

6. Action Level - OSHA establishes Action Levels for exposures to serve as triggers for administrative actions such as implementation of medical surveillance or other administrative controls. The OSHA Action Level is 85 dBA for an eight hour TWA noise exposure. • Exposures > 85 dBA for eight hour TWA require inclusion in a Hearing Conservation Program. Key elements of the program included: exposure monitoring, audiometric testing, use of hearing protection, worker training and record keeping.

7. Begin Date and End Date - The date(s) on which the sample was collected.

8. Begin Time and End Time - The time die sample was collected. We use die 24 hour clock.

CITY_21MC100_0 07320691

NYC-WTC_000234639