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10 Cards in this Set
- Front
- Back
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Sound |
vibrations in the form of waves that travel through fluids (air) and are heard when they enter the ear Fluctuations in atmospheric pressure |
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Wavelength and Frequency |
-Wavelength: distance that a sound travels in one cycle (measured in feet or meters) -Frequency: # of times/second a vibrating body traces one complete cycle of motion (measured in Hz) (audible range is 20-20,000 Hz) -Low frequency = long wave lengths -High frequency = short wave lengths |
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Decibel |
-1/10 of a bel; unit for measuring sound -1 dB is the minimum difference that is perceptible - 60dB + 60dB = 63dB, not 120dB |
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Adding dBs |
-Difference in dBs 0-10: add 3,2,1, or 0 to higher dB value - 0-1 diff. add 3 dB - 2-3 diff. add 2 dB - 4-9 diff. add 1 dB - 10 or more diff. add 0 |
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Noise Weightings (A,B,C) |
- A-weighted is used by ACGIH, OSHA, and NIOSH - A scale is most representative of human hearing. (dBA) |
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Daily Noise Dose (DND): |
90 dBA: 8hrs/day 92 dBA: 6hrs/day 95 dBA: 4hrs/day 97 dBA: 3hrs/day 100dBA: 2hrs/day 102dBA: 1.5hrs/day 105dBA: 1hrs/day 110dBA: 0.5hrs/day 115dBA: 0.25 or less hrs/day
- 5 dB increase in sound, reduce time by half - exposure to diff. noise levels during day: C1/T1 + C2/T2 + C3/T3 Ex. 5hrs/8hrs(90dBA) + 2hrs/6hrs(92dBA) + 1hr/3hrs(97dBA) |
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Continuous & Impact Noise PELs |
-Continuous: above 115dBA not permitted any length of time (intervals of 1 sec. or less is considered continuous) -Impact: (hammering) do not exceed 140dBA (140dBA is considered threshold of pain) |
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OSHA Noise Standard PEL for 8-hour shift |
-8hr PEL at 90dBA. -8 hr TWA of 85 dBA or higher must be placed in a hearing conservation program -
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Health effects of noise exposure |
-Noise-induced hearing loss (cumulative permanent loss of hearing, over time) -acoustic trauma (injury to sensorineural elements of inner ear) one or few exposures to intense impact noise (happens immediately)
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types of noise monitors |
-Sound Level Meter: basic instrument to measure sound pressure levels. contain microphone and amplifier. range of 40-140 dB. -Octave Band Analyzer (OBA): octave represents freq. interval between a given freq. and twice that freq. OBAs evaluate freq. of noise energy -Noise Dosimeters: personal monitoring devices worn by workers to measure personal exposures. Records noise energy exposure during shift of worker. |
