The graph shows the US Department of Labor noise regulation for working without

Question

The graph shows the US Department of Labor noise regulation for working without ear protection. A machinist is in an environment where the ambient sound level is of 85 dB, i.e., corresponding to the 8 Hours/day noise level. The machinist likes to listen to music, and plays a Boom Box at an average level of 86.0 dB. Calculate the INCREASE in the sound level from the ambient work environment level (in dB). 4.75 Compute the intensities from the levels, add them to get the total intensity, then find the total sound level. Note the question asks for the increase. Tries 2/12 A student at a rock concert has a seat close to the speaker system, where the average sound intensity corresponds to a sound level of 114 dB. By what factor does that sound intensity exceed the 1.5- Hours/day intensity limits from the graph? Tries 0/12

Explanation / Answer

(a) total sound level

L = 10 log ( 10 L1/10 + 10 L2/10 )

= 10 log (10 85/10 + 10 86/10) = 88.54 dB

so the INCREASE in the sound level from the ambient work environment level (in dB) is 3.54 dB

(b) the 1.5- Hours/day intensity limits from the graph is 97 dB

assume L1 = 20 log (p1/pref) = 97

p1/pref = 104.85

L2 = 20 log (p2/pref) = 114

p2/pref = 10 5.7

p2/p1 = 10 5.7 / 10 4.85 = 7.079

that sound intensity exceed the 1.5- Hours/day intensity limits from the graph by a factor of 7.079

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