noise pollution · noise pollution chapter 16 what’s the difference between a sound and a noise?...
TRANSCRIPT
Noise PollutionChapter 16
What’s the difference between
a sound and a noise?(Intro & Section 16.3)
Pressure Waves (Section 16.1)
Source
Sound Pressure Level
SPL = 10 log (P2/Po2)
Po = 0.00002 Pa
Units: dB
Typical SPLs
Source SPL (dBA)
Insect wings humming 27
Rain patter on tent 30
Frog chorus (distant) 30
Locomotive (17 mi) 30
Elk eating 31
Jet overflight 44
Tourist car idling 48
Morning birdsongs 50
City traffic 74
Indianapolis Motor Speedway 124
Measurements by Gordon Hempton, “an acoustic ecologist
and sound recordist”
Changes in Sound Energy
Decibel Addition
For n sources of the same dB:
SPLTotal = 10 log n + SPLo
10/10log10 iSPL
TotalSPL
In-Class Activity
Your company is purchasing an additional piece of
manufacturing equipment. You have two choices. One
brand generates 91 dB(A); another brand costs 10%
more but generates 88 dB(A). You determine that the
current level of noise in the production area is 88 dB(A).
The workers are on 8-hour shifts. The OSHA 8-hour
noise limit for the area is 93 dB(A). The company has
been doing well and has thoughts of expanding
production at this location in the near future. Determine
which piece of equipment to purchase.
Perception of Changes
Sources dB Increase Loudness
0.01 -20 1/4x
0.1 -10 1/2x
0.5 -3 Trace
1 0
2 3 Trace
10 10 2x
100 20 4x
1,000 30 8x
10,000 40 16x
Effect of Distance
2
2
1log10
r
rSPL
Point Source
2
1log10r
rSPL
Line Source
Effect of Distance
Point source: SPL = 20 log (D/Do) 6 dB/DD
Line source: SPL = 10 log (D/Do) 3 dB/DD
Hard site: SPL = 10 log (D/Do) 3 dB/DD
Soft site: SPL = 15 log (D/Do) 4.5 dB/DD
Calculating SPL
SPL average from a frequency analysis
N = number of measurements taken
10/10
1log10 iSPL
AvgN
SPL
In-Class ActivityOctave Band (Hz) SPL (dB)
31.5 30
63 40
125 10
250 30
500 128
1000 80
2000 10
4000 2
8000 0
Other Issues(Section 16.2)
Time
LeqSPL
Time Varying SPL
Weightings
Noise Abatement and Control(Sections 16.4 and 16.5)
Who regulates noise levels?
Noise Abatement and Control
What are some options for abating or
controlling traffic noise?
Some Info about Noise Barriers
How effective are they?
When are they considered?
When are they installed?
Of what are they constructed?
Berm
Precast Concrete - 1980
Durisol - 1993
Carsonite - 1994
Wood/Glue Laminate - 1985
Brick
Metal
1984 1985
Light Pollution
Orion: Rural vs. Urban Sky