ME405_Lecture_10

# ME405_Lecture_10 - Office of the Federal Register 1988...

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ME 405 Fall 2006 Professor John M. Cimbala Lecture 10 09/27/2006 Today, we will : Finish our discussion of Section 3.4 – Hearing and Noise Do some example problems Discuss Section 3.5 – Thermal Comfort and Heat Stress Do some example problems Example Given : The noise level of a factory machine is 85 dB at 10 m in free space. To do : Estimate the sound pressure level at a distance of 4.0 ft away when the machine sits in the corner of the building, and all walls are concrete. Solution :

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Example Given : A man stands between two noisy machines on a concrete floor with no walls nearby. Machine 1 has an acoustic power of 0.40 W, and is 1.0 m away to the man’s right. Machine 2 has an acoustic power of 0.50 W, and is 2.0 m away to the man’s left. To do : Estimate the sound pressure level at the man’s ears. Solution :

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Section 3.4.5 – Noise Standards – see Table 3.5 in the text: Table 3.5 ACGIH and OSHA noise limit standards for the workplace (from Internet websites and US

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Unformatted text preview: Office of the Federal Register, 1988). sound intensity (dBA) ACGIH exposure time (hr) OSHA exposure time (hr) 80 24 32 82 16 24.3 85 8 16 88 4 10.6 90 - 8 91 2 7 92 - 6 94 1 4.6 95 - 4 97 0.5 3 100 0.25 2 102 - 1.5 105 - 1 110 - 0.5 115 - 0.25 or less Some typical metabolic rates (for “average” 70-kg man) – see Table 3.6 in the text: Table 3.6 Metabolic rate as a function of physical activity for a 70 kg adult man (abstracted from ASHRAE, 1997). activity metabolic rate (W) metabolic rate (kcal/hr) sleeping 72 62 seated, quiet 108 93 standing, relaxed 126 108 walking about the office 180 155 seated, heavy limb movement 234 201 flying a combat aircraft 252 217 walking on level surface at 1.2 m/s 270 232 housecleaning 284 244 driving a heavy vehicle 333 286 calisthenics/exercise 369 317 heavy machine work 423 364 handling 50-kg bags 423 364 playing tennis 432 372 playing basketball 657 565 heavy exercise 900 774...
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ME405_Lecture_10 - Office of the Federal Register 1988...

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