Unit 5: Noise Calculations
Unit 5: Noise Calculations
Unit 5: Noise Calculations
NOISE CALCULATIONS
HPEO 408
Occupational Health Hazards
EXCHANGE RATE
Theoretically total daily dose is more important than actual exposure levels
For example:
If we start an exposure limit of 85 dBA for 8 hours, we know if we double the
exposure (i.e. 85 dBA + 3 dBA = 88 dBA)
Then the permissible time would be halved (i.e. 8 hours/2 = 4 hours)
Note there are more complex equations available but for this course we will
be using the tables to determine permissible limits
PERMISSIBLE LIMITS
(3dBA EXCHANGE RATE)
Halving Doubling
Noise level Permissible Noise level Permissible
(dBA) Time (hours) (dBA) Time (hours)
61 2048 85 8
64 1024 88 4
67 512 91 2
70 256 94 1
73 128 97 0.5
76 64 100 0.25
79 32 103 0.125
82 16 106 0.0625
85 8 109 0.03125
“NOISE LEVEL” VS. DOSE
For example:
8 hr exposure at the exposure limit is the maximum therefore;
8 hr @ 85 dBA = 100% dose
DOSE CALCULATION
Where:
Step 1: determine permissible exposure times for each activity (Tn) from
permissible limits table
85 dBA = 8 hours
88 dBA = 4 hours
73 dBA = 128 hours
DOSE CALCULATION EXAMPLE CONT.
TWA ESTIMATION FROM DOSE?
REFERENCES FOR NOISE CALCULATIONS
Methods for dealing with non 8-hr work shifts (i.e. Lex)
http
://www2.worksafebc.com/publications/OHSRegulation/GuidelinePart7.asp#Sectio