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!