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 82.0 dB 6 2 90 95 85 105 100 Sound Level (dB) Calculate the INCREASE in the sound level from the ambient work environment level (in dB) Tries 0/12 Submit Answer 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 116 dB. Bý what factor does that sound intensity exceed the 1.5- Hours/day intensity limits from the graph? Tries 0/12 Submit Answer Permissible noise exposure, Hours/day

Answer 1

(a) Ambient sound level = 85 dB Average level = 82 dB Turn dB levels in powers of 1o. To do this simply divide dB level by 10. 85 1018.5) 82 = 108.2) Sound level due to ambient work environment and music is 10 log ( 108 3 + 108 2) = 86.76 dB Increase in Sound level = 86.76-85 Increase = 1.76 dB

(6) For 1.5 Hours per day sound level is 97 dB from graph 116 - 97 = 19 dBV Now 19 dB a 101.9 = 19.4 i sound intensity increase by (79•4 times.

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