Ground Attenuation, Barriers and Distant Receivers

1
Ground Attenuation, Barriers and Distant
Receivers

• Lloyd Herman
• Ohio University

2
Distant receivers
Location 0.4 3.2 km (¼ to 2 mi) from
highway Problem complaints of increased
noise levels after barrier construction
3
California experience

• Hendriks and Hecker 1989
• I-405 in LA
• Receivers 0.3 0.6 km (0.2 0.4 mi)
• Woodward-Clyde Illingworth and Rodkin
• 1994
• I-680 in SF Bay area
• Receivers 0.4 1 km (0.25 0.67 mi)

4
Ohio experience

• I-71 in southern Ohio
• Receivers 0.2 0.5 km (0.1 0.33 mi)
• SR8 in northern Ohio
• Receivers 0.2 0.8 km (0.15 0.5 mi)

5
Survey of 1200 residents

• 35 said noise levels increased
• The most complaints
• 0.2 0.3 km (0.15 0.2 mi)
• located in parallel barrier sections

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Barrier attenuation and path length difference
Receivers
b
Source
d
a
c
7
Sound path
8
Attenuation Mechanisms
Source Level
9
Ground Attenuation
R
S

• Path length difference
• Air to ground impedance ratio
• Angle of incidence

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Ground effect
Source Piercy and Embleton, JASA 61 1403-1418
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Before barrier construction
12
After barrier construction
Source Level
Geo Sprd
Atm
Barrier
Ground
Meas. Level
13
High and Low source levels
 
Site Cinderella
14
High and Low source levels
 
Site Kenwood Meadows
15
High and Low source levels
 
Site Glenover
16
High and Low source levels
 
Site Delray
17
High and Low source levels
 
Site Cooperwood 1
18
High and Low source levels
 
Site Cooperwood 2
19
After barrier construction
Source Level
Geo Sprd
Atm
Barrier
Ground
Meas. Level
20
Parallel barrier degradation
 
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no conclusions!
Ideas, Thoughts, Comments, Questions?