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

Earth at Night

Mexico City

Orion: Rural vs. Urban Sky

Solutions?