PROCEEDINGS of the
23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

Road Traffic Noise Prediction Model “ASJ RTN-Model 2018”
Proposed by The Acoustical Society of Japan– Part 4: Accuracy Verification of a Practical Method for Areas
behind Buildings in Urban Districts
Ken ANAI1; Toshio MATSUMOTO2; Takatoshi YOKOTA3; Shinichi SAKAMOTO4
1
2, 3

Fukuoka University, Japan

Kobayasi Institute of Physical Research, Japan
4

The University of Tokyo, Japan

ABSTRACTThe purpose of this study is to verify the ASJ RTN-Model for application to areas behind buildings, whichis called a practical method in this paper, by comparing the calculated noise levels and the measured onesin urban districts. Two kinds of verification are explained in this paper. For one kind of verification, themaximum noise levels when passing an inspection vehicle at a steady speed on a plane road or a cut-earthroad facing detached residential areas are employed in unit patterns. For the other kind of verification,equivalent noise levels are calculated along a city road by the practical method using road traffic census
data. As a result, the differences between the calculated levels and the measured ones are found to bewithin plus or minus 3 dB for the investigation of the maximum noise levels and within plus or minus 3 dB
to 5 dB for the investigation of the equivalent noise levels. These investigations verify that the practicalmethod for application to areas behind buildings can also be used for various road structures, and that themethod is accurate enough to create noise maps.
Keywords: Road traffic noise, Prediction method, Buildings, Accuracy, Unit pattern, Census data

1. INTRODUCTION
Road traffic noise is reduced in areas behind buildings, because the buildings obstruct the noisepropagation from the road. To calculate the effect of the obstruction of such buildings, theAcoustical Society of Japan presented a method for areas behind buildings as a part of RTN-Model2018. In this paper, the accuracy of the method is verified through investigations that compare
calculated levels and measured ones in urban districts.
Using the method, the correction values for the amounts of noise reduced by the buildings arecalculated from unit patterns of point sound sources, that is the general rule of the RTN-Model 2018.
The number of parameters required to calculate the correction amounts is four; this is smaller thanthe eight that were required for RTN-Model 2013. The aim of the method in RTN-Model 2018 is tosimplify the calculation process (1, 2); it is called “a practical method based on the point soundsources.” The practical method includes processes for the omission of part of the calculation, andthese omission processes can, in turn, reduce the calculation hours. However, the advanced
calculation method (3) in RTN-Model 2013 is still recommended in certain situations, for example,
when the unit patterns must be calculated more correctly for planning countermeasures against noise.
Two kinds of verification are explained in this paper; one involves the unit patterns behindbuildings when passing an inspection vehicle on a plane road or a cut-earth road and the other
involves equivalent noise levels based on road traffic census data.

1

anai@fukuoka-u.ac.jp
matsumoto@kobayasi-riken.or.jp
3t-yokota@kobayasi-riken.or.jp
4sakamo@iis.u-tokyo.ac.jp
23712

2. VERIFICATION BY MAXIMUM NOISE LEVELS IN UNIT PATTERNSUnit patterns in areas behind buildings are verified for the situation in which an inspection
vehicle runs on a plane road or a cut-earth road at a steady speed. District-M (4) and district-Sa are
selected as the intended areas facing a plane road, and district-Sp is selected as the area facing a
cut-earth road.
The inspection vehicles for district-M are a motor vehicle and a motorcycle. In districts-Sa and-Sp, only the motor vehicle is employed. The motor vehicle runs on a 3,000-cc diesel engine; it has a
one-box design and two-wheel drive. The motorcycle has a 250-cc cowling engine and a genuine
muffler.
2.1 Estimation of Acoustic Power Levels
The methods of maximum noise level and squared integrals are commonly used for estimating theacoustic power levels of vehicles. However, it is difficult to estimate the acoustic power levels of
vehicles in areas with detached residences using these methods. This is because road lanes are few innumber in these areas, the offset distance to a measuring point from the road is short and the noise
sources of the vehicle are not assumed to be coming from just one point.
It would be better, therefore, to realistically estimate not only the power levels, but also thepassing speeds and positions, because the estimated parameters can be used later on for calculating
the unit patterns of the noise levels. In this study, the passing speed, the position and the power levelof a single inspection vehicle are estimated by the least squares method in parallel with the measured
unit patterns beside the road.
The noises emitted by a vehicle come from the engine, the tires and the muffler. In this study,
however, just two noise sources are assumed. The total power level of the inspection vehicle is a
simple energy summation of two sources on the assumption that the sources exist at the front and therear of the vehicle, respectively, and have the same acoustic power.
M

M

SP

M

Figure 1 – Arrangement of residences and intended points in district-M facing a plane road90

LA [dB]

80

Inferred
Measured

Motor vehicle (Van type)
Point M-j

70

60

LW A LMS = 89.5 dB + 89.5 dB
50

40
12:43:09

d road LMS, Mj = 2.4 m
v LMS = 9.9 m/s

12:43:11

12:43:13

12:43:15

Time ( h:m:s )Figure 2 – Comparison of unit patterns based on estimated and measured power levels at point M-j at theend of the road3713

In the investigation of district-M, illustrated by the layout plan in Fig. 1, the results for thevehicle are a passing speed of v LMS = 9.9 m/s and a position of d road LMS = 2.4 m, and the power levelof one source is 89.5 dB. The position of 2.4 m indicates that the passing vehicle is located aroundthe center of a near side lane. The estimated and measured unit patterns after 6.0 seconds have
similar characteristics, as shown in Fig. 2. The total power level is 92.5 dB.
The results for the motorcycle are a total power level estimated to be 97.4 dB, a passing speed of
12.8 m/s and a position of 3.2 m distance from point M-j. The position indicates that the inspection
motorcycle passes near the centerline of the near side lane. The results are considered to be valid.
2.2 Unit Patterns from a Plane Road
In order to verify the practical areas as models behind buildings for detached residences facing aplane road, the calculated unit patterns are compared with the measured ones in two districts,
referred to as M and Sa.
2.2.1 Unit Patterns in District-M
In district-M, there are front yards and carports between the residences, and the buildings arearranged spaciously. Nine investigation points, points M-a to M-i, are placed along public roads
behind buildings. The single inspection vehicle or motorcycle on the plane road travels in the
direction from point M-i to point M-a. Unit patterns for the investigation points calculated by thepractical method are compared with the measured ones by omitting a part of the calculation (5). In
addition, errors in appearance of the unit patterns calculated by the omitted calculation are verified.
The acoustic power levels are estimated by the measured unit pattern for point M-j, which is locatedat the end of the road. The power levels of the inspection vehicle and the motorcycle are 97.4 dB and
92.5 dB, respectively.
Discrete source points are arranged at the closest point on the road as a reference and at intervalsof d road,x . Comparisons of the calculations with the measurements are given in Figs. 3 and 4 asexamples of the unit patterns of the motorcycle and the vehicle, respectively. Investigation points
M-a and M-i have a clear view of the road from both points. However, investigation point M-c does
not have any view of the road at all. The calculated maximum noise levels at every point in Figs. 3
and 4 approximately correspond to the measured ones irrespective of having a view of the road ornot.
Next, the errors in appearance of the unit patterns calculated by the omitted practical method are
explained for investigation points M-d and M-f. Two unit patterns are plotted in Fig. 5 with bullet
and circle symbols that are calculated by the omitted practical method and by the original one,respectively. The values calculated by the omitted method appear outside of a zone bounded by
dot-and-dash lines in Fig. 5. The largest errors appear very close to the dot-and-dash lines and can befound on horizontal axis k=-2. The omitted method calculates insignificantly smaller values than theoriginal one. However, the errors are never more than 0.5 dB, and the influence of the errors on theequivalent level is exceedingly small.
80

Omitted practical meth.
Measured

60

50

40

30
12:27:35

70

LA [dB]LA [dB]7080
Motorcycle (250 cc)
Point M-c

Motorcycle (250 cc)
Point M-a

Omitted practical meth.
Measured

60

50

40

12:27:45

12:27:55

12:28:05

Time ( h:m:s )12:28:15

30
12:27:35

12:27:45

12:27:55

12:28:05

12:28:15

Time ( h:m:s )Figure 3 – Comparison of calculated unit patterns by the practical method and measured ones in district-M
under conditions of the motorcycle passing

3714

80

80

70

70

60

50

Motor vehicle (Van type)
Point M-c

Omitted practical meth.
Measured60

LA [dB]LA [dB]

Omitted practical meth.
Measured

Motor vehicle (Van type)
Point M-i

50

40

40

30
12:42:50

12:43:00

12:43:10

12:43:20

12:43:30

30
12:42:50

12:43:00

Time ( h:m:s )12:43:10

12:43:20

12:43:30

Time ( h:m:s )Figure 4 – Comparison of calculated unit patterns by the practical method and measured ones in district-M
under conditions of the motor vehicle passing

Omitted practical Method
Practical Method

Point M-d

5 dB

LA [dB]LA [dB]

5 dB

Omitted practicalmethodPractical method

Point M-f

ξ · d sp < 22.1

-6

-4

-2

0

ξ · d sp < 22.1

2

4

6

-6

Scattered source points No. k

-4

-2

0

2

4

6

Scattered source points No. k

Figure 5 – Influence of the omitted calculation of the practical method on the unit patterns
2.2.2 Unit Patterns in District-Sa
An arrangement of residences and investigation points in district-Sa is illustrated in Fig. 6. Inorder to verify the omitted practical method for the area facing a plane road, the calculated unit
patterns are compared with the measured ones. The acoustic power level of the inspection vehicle is100.3 dB; it is estimated from a unit pattern at point Sa-j. The passing speed of the vehicle and the
distance from point Sa-j are also estimated as 10.2 m/s and 2.6 m, respectively.

30 m

k=-3

k=-2

k=-1

k=0

k=1

k=2

k=3

Sa-j
Sa-a

Sa-b Sa-c Sa-d Sa-eSa-f Sa-g Sa-h Sa-i

Figure 6 – Arrangement of residences and intended points in district-Sa facing a plane roadAs examples of verified unit patterns, the comparison results for points Sa-e and Sa-a are drawn
in Fig. 7. The calculated unit patterns are almost consistent with the measured ones at every

3715

investigation point, especially for the maximum noise levels.
All the maximum noise levels at the districts with plane roads, which are explained in sections
2.2.1 and 2.2.2, are shown in Fig. 8 in a distribution chart of the calculated values against themeasured values. There are nine values each for the vehicle and the motorcycle in district-M, andnine values for the vehicle in district-Sa. All the calculated values have a high correlation with themeasured ones, and the differences between them are around plus or minus 3.0 dB.
On the basis of these results, the omitted practical method was verified as being capable ofcalculating unit patterns relevantly in areas behind buildings, especially for large noise levels whenvehicles are close to the investigation points.
80
Measured
Omitted practical meth.

70

60

LA [dB]LA [dB]7080
Motor vehicle (Van type)
Point Sa-e

50
40
30
11:26:40

Motor vehicle (Van type)
Point Sa-a

Measured
Omitted practical meth.

60
50
40

11:27:00

11:27:20

11:27:40

11:28:00

30
11:26:40

11:27:00

Time (h:m:s)

11:27:20

11:27:40

11:28:00

Time (h:m:s)

Figure 7 – Comparison of calculated unit patterns by the practical method and measured ones in district-Sa
under conditions of the motor vehicle passing

Calculated LA, F max [dB]65

Motorcycle (dist-M, N=9)Motor vehicle (dist-M, N=9)

60

55

50

45
Motor vehicle (dist-Sa, N=9)
40
40

45

50

55

60

65

Measured LA, F max [dB]

Figure 8 – Correspondence of maximum noise levels by the practical method with measured ones in areas
behind buildings facing a plane road, called district-M and district-Sa
2.3 Unit Patterns from Cut-Earth Road in District-Sp
The road facing district-Sp is a two-way street with a gentle slope; therefore, part of the road is a
cut-earth road, as illustrated in Fig. 9. Some investigation points would be influenced by thediffraction effects at the wedge of the cut-earth.
As examples of the investigation points that would be calculated by considering the diffraction
effects (6), unit patterns at points Sp-h and Sp-i are drawn in Fig. 10. In this figure, the calculated
values for the condition in which the road surface height is the same as that of the ground of theresidences are shown by circle symbols. For the condition in which the diffraction by the wedge ofthe cut-earth is corrected, the calculated values are shown by bullet symbols in Fig. 10. Five noise

3716

levels out of the 45 predicted ones were corrected with the diffraction effects, as shown in the
distribution chart in Fig. 11.
These results demonstrate that the omitted practical method can be applied to areas facing a
cut-earth road by means of the correction of the diffraction effects on the wedge and the attenuation
by buildings. The difference in levels between the calculated values and the measured ones decreased
by within plus or minus 3.0 dB.

Sp-i Sp-h Sp-g Sp-f

k =-2

Sp-j

k =2

k =1

k =0

k =-1

Sp-e Sp-d Sp-c Sp-b Sp-a

30 m

Figure 9 – Arrangement of residences and intended points in district-Sp facing a cut-earth road that is theshaded part on this figure
80
Measured
Regarded as plane road
Diffraction corr.

70

60

LA [dB]LA [dB]7080
Motor vehicle (Van type)
Point Sp-h5040Motor vehicle (Van type)
Point Sp-i

Measured
Regarded as plane road
Diffraction corr.

60
50
40

30
13:55:37

13:55:47

13:55:57

13:56:07

13:56:1730
13:55:37

13:55:47

Time (h:m:s)

13:55:57

13:56:07

13:56:17

Time (h:m:s)

Figure 10 – Comparison of calculated unit patterns by the practical method and measured ones in
district-Sp under conditions of the motor vehicle passing

Calculated LA, F max [dB]60

Regarded as plane road (N=5)
Diffraction corr. (N=5)

55

50

45

40

35
35

40

45

50

55

60

Measured LA, F max [dB]

Figure 11 – Correspondence of maximum noise levels by the practical method and diffraction correction
with the measured ones in areas behind buildings facing a cut-earth road, called district-Sp

3717

3. VERIFICATION OF EQUIVALENT NOISE LEVELS FROM CENSUS DATA
The estimation of the exposed level of road traffic noise was conducted in Saitama City (7) byutilizing the practical method of RTN-Model 2018.
Equivalent noise levels are calculated in areas behind buildings facing plane roads, called A andB, for the purpose of making a comparative verification of the calculated values with the measured
ones and then extending it to make a noise map. The arrangements of residences around roads A and
B are shown in Fig. 12. In this calculation, road traffic census data are used for estimating the factorsof the traffic conditions. As for the results of the estimations for road-A, the hourly traffic volumes
are 3,370 small-size vehicles and 996 large-size vehicles, and the average passage speed is 36.7 km/h.
The acoustic power levels of the vehicles are determined to be 92.7 dB for the small-size vehicles
and 100.1 dB for the large-size vehicles on the assumption that the vehicles are running at a steadyspeed. As for the results of the estimations for road-B, the hourly traffic volumes are 768 small-size
vehicles and 64 large-size vehicles, and the average passage speed is 19.9 km/h. The acoustic power
levels are determined to be 95.3 dB for the small-size vehicles and 101.8 dB for the large-size
vehicles on the assumption that the vehicles are not running at a steady speed due to the successive
traffic signals along road-B.
Figure 13 shows that the differences in the calculated values and the measured ones on theintended road-A and road-B are around plus or minus 3 dB and 5 dB, respectively.
Road-A

A2 A1

A3
A1A2

Road-B

B2
B1

Elevated
highway
-

C1

D2D1
D3
C2C1
C3

C2

D1

D2
K

B2
B1

E1

Plane roadE2

Figure 12 – Arrangement of residences and intended points for verification of equivalent noise levels
calculated with census data80

Calculated LAeq [dB]75

Road-A (N=11)
Road-B (N=11)

70
65
60
55
50
50

55

60

65

70

75

80

Measured LAeq [dB]

Figure 13 – Correspondence of equivalent noise levels by the practical method and census data with themeasured ones in areas behind buildings facing a plane road3718

4. CONCLUSIONSThe practical method of RTN-Model 2018 for areas behind buildings was made to be moreconvenient than RTN-Model 2013 by reducing the parameters necessary for the calculation.
Acceptable results for the verification were explained in this paper by examples in urban districts.
The practical method had a certain degree of accuracy in areas behind buildings for every
verification with the maximum noise level in unit patterns and the equivalent noise level based on theroad traffic census data.
The practical method of RTN-Model 2018 is regarded as an accurate and convenient method for
calculating equivalent noise levels in areas behind buildings.

ACKNOWLEDGEMENTS
The authors gratefully acknowledge Mr. Shunsuke Kouda of Kobayasi Institute of PhysicalResearch, Mr. Ryosuke Kazama of RION Co. and many students belonging to Kyushu Institute ofTechnology or Fukuoka University in Japan for their support of the field surveys. The authors also
acknowledge local governments, self-governing bodies and residents, who are owners or users of theinvestigated roads and districts.

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