Sound-A pressure variation (wave) that travels through air and is detected by the human ear
Physics of Sound
Noise-Excessive or unwanted sound which potentially results in annoyance and/or hearing loss (can be from occupational and/or non-occupational sources)
-Physical manifestation of noise is a pressure wave–Caused by vibrating surfaces
-Noise-exposed workers are employed in wide range of industries
(Agriculture, mining, construction, manufacturing, transportation, military)
-The two factors that determine how hazardous noise is are:
•Intensity (Loudness) measured in dBA
•Time of Exposure measured in Hours and Minutes
-The louder the noise, the more hazardous it is. Also, the longer the exposure time, the more hazardous the noise is.
-A “Noise Dose” combines both loudness and time and is a convenient way of describing the relative hazard of the noise.
Loudness is measured using a logarithmic scale. This
means that a 10 decibel increase does not simply add 10
to the previous level. It multiplies the previous level by 10.
Threshold of Hearing 0 dBA
Quiet Room 45 dBA
Conversation 55 dBA = 45 dBA x 10
Car (50 mph at 50 ft) 65 dBA = 45 dBA x 100
End Loader (In Good Cab) 75 dBA = 45 dBA x 1,000
Haul Truck (In Good Cab) 85 dBA = 45 dBA x 10,000
Crusher 95 dBA = 45 dBA x 100,000
Old Dozer (No Cab) 105 dBA = 45 dBA x 1,000,000
Air Track Drill (No Controls) 115 dBA = 45 dBA x 10,000,000
115 dBA has 10 million times more sound energy than 45 dBA and is
capable of causing 10 million times more damage to hearing.
Allowable Noise exposure is based on Noise Dose.
Noise Dose is expressed as a percentage of the allowable
limit. How high it goes depends on both noise intensity
and time of exposure to noise.
Louder (More dBA) = More Noise Dose
Longer (More Time) = More Noise Dose
Absolute Quiet = 0% Noise Dose.
85 dBA for 8 Hrs = 50% Noise Dose.
90 dBA for 8 hrs = 100% Noise Dose.
95 dBA for 8 Hrs = 200% Noise Dose.
95 dBA for 12 Hrs = 300% Noise Dose.
Different combinations of Loudness and Time can produce the same Noise Dose.
The following combinations can all produce about 75% Noise Dose.
Loudness is measured using a logarithmic scale. This
means that a 10 decibel increase does not simply add 10
to the previous level. It multiplies the previous level by 10.
Threshold of Hearing 0 dBA
Quiet Room 45 dBA
Conversation 55 dBA = 45 dBA x 10
Car (50 mph at 50 ft) 65 dBA = 45 dBA x 100
End Loader (In Good Cab) 75 dBA = 45 dBA x 1,000
Haul Truck (In Good Cab) 85 dBA = 45 dBA x 10,000
Crusher 95 dBA = 45 dBA x 100,000
Old Dozer (No Cab) 105 dBA = 45 dBA x 1,000,000
Air Track Drill (No Controls) 115 dBA = 45 dBA x 10,000,000
115 dBA has 10 million times more sound energy than 45 dBA and is
capable of causing 10 million times more damage to hearing.
Allowable Noise exposure is based on Noise Dose.
Noise Dose is expressed as a percentage of the allowable
limit. How high it goes depends on both noise intensity
and time of exposure to noise.
Louder (More dBA) = More Noise Dose
Longer (More Time) = More Noise Dose
Absolute Quiet = 0% Noise Dose.
85 dBA for 8 Hrs = 50% Noise Dose.
90 dBA for 8 hrs = 100% Noise Dose.
95 dBA for 8 Hrs = 200% Noise Dose.
95 dBA for 12 Hrs = 300% Noise Dose.
Different combinations of Loudness and Time can produce the same Noise Dose.
The following combinations can all produce about 75% Noise Dose.
84 dBA for 14 Hrs = 76%
85 dBA for 12 Hrs = 75%
87 dBA for 9 Hrs = 74%
88 dBA for 8 Hrs = 76%
93 dBA for 4 Hrs = 76%
95 dBA for 3 Hrs = 75%
98 dBA for 2 Hrs = 75%
103 dBA for 1 Hr = 76%
108 dBA for 30 Min = 76%
113 dBA for 15 Min = 76%
