Question

Q2(b) Three boilers located next to each other give individual sound pressure levels of 108, 96 and 111 dB, respectively.

(i) Determine the total sound pressure level when all of the boilers are switched on together

(ii) Noise measurement was made at 1 m from the noise source with a reading of 105 dB. If the workstation is located at 4 m from the noise source, estimate the sound pressure level received by the workers at the workstation. The workers needs to be at the workstation for 8 hours daily.

(iii) Based from your answer 1n Q2 (b)(ii), suggest the allowable exposure time the workers can be at the workstation daily according to 3 dB exchange rate.

Answer 1

Concept used for part(iii)

The dose limit uses a 3dB time-intensity tradeoff. For every 3dB increase in noise level, the allowable exposure time is doubled as shown in the table:

Average Sound Exposure Levels Needed to Reach the

Maximum Allowable Daily Dose of 100%

Time to reach 100% noise dose	Exposure level per NIOSH REL
8 hours	85 dB(A)
4 hours	88 dB(A)
2 hours	91 dB(A)
60 minutes	94 dB(A)
30 minutes	97 dB(A)
15 minutes	100 dB(A)