Ground Attenuation, Barriers and Distant Receivers
Lloyd Herman
Ohio University
Distant receivers
Location: 0.4 – 3.2 km (¼ to 2 mi) from highway
Problem: complaints of increased noiselevels after barrier construction
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)
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)
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
Source
Receivers
a
b
cd
Barrier attenuation and path length difference
Sound path
SourceLevel Geo Sprd
AtmBarrier
GroundMeas. Level
Attenuation Mechanisms
Ground Attenuation
SR
• Path length difference
• Air to ground impedance ratio
• Angle of incidence
Ground effect
Source: Piercy and Embleton, JASA 61 1403-1418
Before barrier construction
Geo Sprd
AtmBarrier
GroundMeas. Level
SourceLevel
After barrier construction
Geo Sprd
AtmBarrier
Ground Meas. Level
SourceLevel
High and Low source levels
40
45
50
55
60
65
70
75
80
180 210 240 270 300 330 360Distance from Barrier (m)
dBA
H
L
Site: Cinderella
High and Low source levels
40
45
50
55
60
65
70
75
80
180 210 240 270 300 330 360Distance from Barrier (m)
dBA
H
L
Site: Kenwood Meadows
High and Low source levels
40
45
50
55
60
65
70
75
80
180 200 250 300 360 420 480
Distance from Barrier (m)
dbA
H
L
Site: Glenover
40
45
50
55
60
65
70
75
80
180 210 240 270 300 330 360
Distance from Barrier (m)
dBA
H
L
High and Low source levels
Site: Delray
High and Low source levels
40
45
50
55
60
65
70
75
80
180 210 240 270 300 330 360Distance from Barrier (m)
dBA
H
L
Site: Cooperwood 1
High and Low source levels
40
45
50
55
60
65
70
75
80
180 210 240 270 300 330 360
Distance from Barrier (m)
dBA
H
L
Site: Cooperwood 2
After barrier construction
Geo Sprd
AtmBarrier
Ground Meas. Level
SourceLevel
Parallel barrier degradation
0
0.5
1
1.5
2
2.5
3
3.5
4
0 30 60 120 180 240 300 420
Microphone Distance From Barrier (m)
Pa
rall
el B
arr
ier
Deg
rad
ati
on
(d
B)
Cooperwood
Jolain
Baywind
Glenover
Delray
Castleford
Ideas, Thoughts, Comments, Questions?
…no conclusions!