1. Three workers (8-hour work shift) were monitored for work in different areas of a facility using calibrated noise dosimeters. The results are summarized in the following table.
Time for Monitoring Worker 1 Worker 2 Worker 3
3 hours 80.5 dBA 98.5 dBA 92.5 dBA
2 hours 81.0 dBA 86.5 dBA 85.0 dBA
2 hours 82.0 dBA 84.5 dBA 83.5 dBA
1 hour 95.0 dBA 83.5 dBA 80.0 dBA
2.
3.
a. Calculate the 8-hour time-weighted average (TWA) noise exposure for each of the three workers.
4. b. Summarize which (one) of the exposures exceeds OSHA's permissible exposure limit (PEL) and/or action level for noise.
5. c. Discuss what factors about the noise monitoring may have affected the accuracy of the noise measurements.
Show your work for all mathematical calculations. Please refer to Appendix A to 29 CFR 1910.95 for assistance on how-to solve this problem
To calculate the 8-hour time-weighted average (TWA) noise exposure for each worker, we need to follow the steps outlined in Appendix A to 29 CFR 1910.95. The formula to calculate TWA is:
TWA = 10 * log10[(T1/8) * (10^(L1/10)) + (T2/8) * (10^(L2/10)) + ... + (Tn/8) * (10^(Ln/10))]
Where:
- T1, T2, ..., Tn are the durations of exposure in hours
- L1, L2, ..., Ln are the measured dBA noise levels
Let's calculate the TWA for each worker:
Worker 1:
(3/8) * (10^(80.5/10)) + (2/8) * (10^(81.0/10)) + (2/8) * (10^(82.0/10)) + (1/8) * (10^(95.0/10))
= (0.375) * (10^8.05) + (0.25) * (10^8.1) + (0.25) * (10^8.2) + (0.125) * (10^9.5)
= 16.943 + 5.012 + 5.622 + 158.11
= 185.687
Worker 2:
(3/8) * (10^(98.5/10)) + (2/8) * (10^(86.5/10)) + (2/8) * (10^(84.5/10)) + (1/8) * (10^(83.5/10))
= (0.375) * (10^9.85) + (0.25) * (10^8.65) + (0.25) * (10^8.45) + (0.125) * (10^8.35)
= 1181.15 + 5.892 + 4.496 + 4.302
= 1195.84
Worker 3:
(3/8) * (10^(92.5/10)) + (2/8) * (10^(85.0/10)) + (2/8) * (10^(83.5/10)) + (1/8) * (10^(80.0/10))
= (0.375) * (10^9.25) + (0.25) * (10^8.5) + (0.25) * (10^8.35) + (0.125) * (10^8)
= 412.54 + 3.162 + 2.828 + 1.585
= 420.115
Now let's move on to the next part:
b. To determine if any of the exposures exceed OSHA's permissible exposure limit (PEL) or action level for noise, we need to refer to the regulations provided in 29 CFR 1910.95. The PEL for noise exposure is 90 dBA for an 8-hour work shift, and the action level is 85 dBA.
Comparing the calculated TWA for each worker, we find:
Worker 1: 185.687 dBA (exceeds both PEL and action level)
Worker 2: 1195.84 dBA (exceeds both PEL and action level)
Worker 3: 420.115 dBA (exceeds both PEL and action level)
Therefore, all three workers have noise exposures that exceed the permissible exposure limit and action level.
c. Factors that could have affected the accuracy of the noise measurements include calibration issues with the dosimeters, placement of the dosimeters on the workers, interference from other sources of noise, and variations in the workers' positions or distance from the noise sources during monitoring. It's important to ensure proper calibration, correct dosimeter placement, and minimize potential sources of interference to obtain accurate noise measurements.