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

Comparison of ASJ RTN-Model 2013 and the Harmonoiseengineering model under thick barrier configurations
Takuya OSHIMA1; Azusa HOSHIKAWA2; Yumi KUROSAKA2
1
2

Faculty of Engineering, Niigata University, Japan

Graduate School of Science and Technology, Niigata University, Japan

ABSTRACTEngineering models for environmental noise are developed in many countries under different backgrounds.
Such differences make each model have different characteristics. In European countries, comparative
studies have been carried out to illustrate the characteristics of models such as Nord2000, Harmonoise and
CNOSSOS-EU. However, comparison of the Japanese road traffic noise model, ASJ RTN-Model 2013, toanother model has seldom been made. This is probably because the ASJ model uses A-weighted levels
throughout the calculation process, unlike European models that use either octave-band or
one-third-octave-band levels. In this study, a methodology to derive consistent quantities between the ASJ
model and the European Harmonoise model is established. The methodology is applied to thick barrier test
cases that are included in a Harmonoise deliverable. At the same time, finite-difference time-domain
simulations are carried out to obtain reference solutions. A-weighted source power levels between the twomodels are found to be larger for the light vehicle of the ASJ model. Comparison between each model andthe reference solutions weighted by each source spectrum agree well for both models. The final A-weighted
levels obtained by both models agree within a 2 dB difference.
Keywords: Source power spectrum, Source directivity, Diffraction model

1. INTRODUCTION
Engineering models for environmental noise have been developed in many countries under
different backgrounds. Such differences make each model have different characteristics. In European
countries, comparative studies have been carried out in open literature to illustrate the characteristics
of models such as Nord2000 (1), Harmonoise (2) and CNOSSOS-EU (3). By taking various forms of
critical reviews (4, 5) and demonstrative approaches (6, 7, 8, 9), those studies provide insights about
the direction towards which a new model should be developed, and thorough validations of a newly
developed model. In Japan, there has been revisions of a road traffic noise model since 1975, called
ASJ Road Traffic Noise (ASJ-RTN) Model, developed by the Acoustical Society of Japan. Since
1993, the ASJ model has been revised in a cycle of 5 years. However, in spite of such a long history,
the characteristics of the ASJ models in comparison with other models have seldom been discussed
in open literature. One of the probable reasons is that the ASJ models use A-weighted overall levels
throughout the calculation process, unlike other models (in particular the European models) that use
either octave-band or one-third-octave-band levels.
In this study, the second latest revision of the ASJ model, ASJ RTN-Model 2013 (10) (referred toas the ASJ model hereafter), is compared with the European Harmonoise engineering model (referred
to as the Harmonoise model), which is the predecessor of the current CNOSSOS-EU model, under asimple configuration of a thick barrier along a straight road. The 2013 version of the ASJ model isused because the 2018 version was not yet available at the time when the main part of this study was
conducted. The Harmonoise model is chosen because there are many open publications that discuss
the development process, details, validation, and test cases of the model. A methodology to deriveconsistent quantities between the ASJ model and the Harmonoise model, such as the single-vehicle
A-weighted power level, is established to make strict comparisons between the two models. The
methodology is applied to thick barrier test cases that are included in a Harmonoise deliverable. At
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oshima@eng.niigata-u.ac.jp

the same time, finite-difference time-domain simulations are carried out to obtain reference solutions.
Then, comparisons of the characteristics of source power modeling, attenuation by diffraction andfinal predicted A-weighted equivalent sound pressure level are made.

2. OUTLINES OF THE MODELS
Outlines of the models and a methodology to derive consistent quantities between both models arebriefly described in this section. The comparisons are made in A-weighted overall levels, as the
A-weighted level can be derived from octave-band levels but the opposite is not possible. Thus, as
stated later, several steps are added to the calculation procedure of the Harmonoise model to obtain
the A-weighted overall levels.
2.1 The ASJ Model
A diagram of a part of the calculation procedure of the ASJ model relevant to this study is shownin Figure 1. First, a source and receiver configuration is given as input. The source road is divided
into segments, and a point source i is set at the middle of each segment. The A-weighted source
power level of source point i, L WA,i , is calculated from the running mode of vehicles, running speed V,
and the source directivity ΔL dir for each vehicle category shown in Table 1. Then, the total
attenuation ΔA A,i of the geometric attenuation and the attenuation by diffraction owing to the thickbarrier is calculated. The A-weighted sound pressure level (SPL) by source i, L A,i , is calculated asfollows.
LA,i = LWA,i − ΔAA,i(1)
Running mode of vehicles
Vehicle speed V
Source directivity ΔLdir

Setting of source and receiver configuration

Single-vehicle A-weighted power level
for a point source, LWA,iGeometric attenuation
Attenuation by diffraction

Total attenuation, ΔAA,iA-weighted sound pressure level (SPL)
by a point source, LA,iRunning speed V
Source segment lengthSingle-event sound exposure level, LAE

Traffic volume Q

Equivalent continuous A-weighted SPL, LAeq

Figure 1 – Calculation procedure of the ASJ model. Underlined variables are calculated ones whereas
non-underlined variables are given as input
Table 1 – Vehicle categories
Model

ASJ
Two-category
Heavy

CategoryLight

Four-category
Large-sizedMedium-sized
Small-sized
Passenger–
Motorcycles

Harmonoise
Heavy
Medium heavy
Light
Other heavy
Two-wheelers

After calculating L A,i for all point sources, the single-event sound exposure level, L AE by a single
vehicle pass-by along the source road is calculated using L A,i for all point sources, the vehicle speed
V and the source segment length. Finally, the equivalent continuous A-weighted SPL, L Aeq , iscalculated using L AE and the traffic volume Q.

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2.2 The Harmonoise Model
A diagram of a part of the calculation procedure of the Harmonoise model relevant to this study
and additional steps to obtain consistent quantities with the ASJ model is shown in Figure 2. First, asource and receiver configuration is given as input. The source road is divided into segments and two
subsources, each of which is at a height h s above the ground, are set at the middle of each segment i.
The height of one of the two subsources is h s = 0.01 m and another is either 0.30 m for a light vehicle
or 0.75 m for a medium-heavy and a heavy vehicle. The source power level for a single-vehicle
subsource, L' W,i,hs , is calculated from the vehicle speed V, the source directivity C dir . Calculation of
the total power level for a subsource, L W,i,hs , follows by using L' W,i,hs , the vehicle speed V, the traffic
volume Q and the segment length. Then, the total attenuation ΔA H,i,hs is calculated from thegeometric attenuation and the excess attenuation including attenuation by diffraction and ground.
The one-third-octave-band SPL for a subsource, L eq1h,i,hs , is calculated as(2)
Leq1h,i,hs = LW ,i,hs − ΔAH,i,hs
Vehicle speed V
Source directivity Cdir
Running speed V
Traffic volume Q
Segment length

Setting of source and receiver configuration

Single-vehicle power level
for a subsource, L'W,i,hs

Geometric attenuation
Excess attenuation

Total attenuation, ΔAH,i,hs

(a)
(b)
(c)
Total power level for a subsource, LW,i,hs(c)One-third-octave-band SPL for a subsource, Leq1h,i,hs
One-third-octave-band SPL for all subsources and all segments, Leq1h
A-weighted SPL for all subsources and all segments, LAeq1h(a) Single-vehicle A-weighted power level for all subsources in source point i, LWA,HN,i(b) A-weighted source directivity, CdirA(c) A-weighted single-vehicle SPL for all subsources in source point i, LA,HN,iFigure 2 – Calculation procedure of the Harmonoise model. Underlined variables are calculated ones
whereas non-underlined variables are given as input
The one-third-octave-band SPL for all subsources and all segments, L eq1h , is calculated byincoherent summation of L eq1h,i,hs over all subsources and all segments. Finally, the A-weighted SPL
for all subsources and all segments, L Aeq1h , is computed by summation of L eq1h with A-weighting
correction added over all bands.
The excess attenuation ΔA H,i,hs is calculated using the official Harmonoise point-to-point (P2P)
library (11) version 2.022.
2.3 Additional Steps for Obtaining Consistent Quantities between the Models
The vehicle categories defined in each model are associated as shown in Table 1. The large-sized
and medium-sized vehicles in four-category classification in the ASJ model are associated with theheavy and medium-heavy vehicles of the Harmonoise model, respectively. The light vehicle in the
ASJ model is associated with the light vehicle in the Harmonoise model. Under the association, threesteps marked as (a)–(c) in Figure 2 are added to the calculation procedure of the Harmonoise model
to obtain consistent quantities with the ASJ model. Step (a) calculates the single-vehicle A-weighted
power level for all subsources in source point i, L WA,HN,i (HN stands for the Harmonoise model
hereafter), by incoherent summation of L' W,i,hs over all subsources and all bands with the A-weights
applied. The L WA,HN,i is considered to be comparable with L WA,i of the ASJ Model. Step (b) calculates
the A-weighted source directivity, C dirA as

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ʹ
ʹ
CdirA = LWA,dir
− LWA

(3)
where L' WA,dir is the A-weighted incoherent summation of all bands and all subsources of L' W,i,hs withthe source directivity C dir applied, and L' WA is the same but without application of the source
directivity. In calculating C dirA , directivity angles defined by the ASJ and the Harmonoise models,(ϕ A , θ) and (Ψ, ϕ H ) shown in Figure 3, respectively, are associated with the help of an auxiliary
variable Θ by
φ A = tan −1 [(cosΘ) / (tan Ψ)] ,(4)

θ = tan −1 (sin φ A tan Θ) (φ A ≠ 0) ,

(5)

!

(6)
Θ = 90 − φ H .
The C dirA is considered to be comparable with ΔL dir of the ASJ model. Step (c) calculates the
A-weighted single-vehicle SPL for all subsources in source point i, L A,HN,i . For this, theone-third-octave-band SPL for a single-vehicle subsource, L HN,i,hs is calculated by
LHN,i,hs = LWʹ ,i,hs − ΔAH,i,hs(7)Then, L A,HN,i , is obtained by incoherent summation of L HN,i,hs over all subsources and all bands with
the A-weights applied. The L A,HN,i is considered to be comparable with L A,i of the ASJ model.

A

P

θ

P

S

S Θ

Ψ

H

Road
(a) ASJ RTN-Model 2013

Road(b) Harmonoise

Figure 3 – Definitions of the directivity angles in the ASJ and the Harmonoise models. S and P are thesource and the receiver, respectively

3. NUMERICAL EXPERIMENTS
3.1 Test Cases
Cases 01 and 05 included in a collection of Harmonoise test cases (12) are used in this study. The
configurations of Cases 01 and 05 are a straight road in a semi-free field as shown in Figure 4, and a
thick barrier along a straight road as shown in Figure 5, respectively. Case 05 has two patterns ofbarriers heights h b = 8 m and 15 m. The patterns are called Maps 11 and 12, respectively. In bothcases, the source road with a length of 2 000 m is placed along y-axis. The source road has Lanes 1
and 2 with a 10 m interval and with vehicles running towards the negative and positive direction of
the y-axis, respectively. Receiver P is placed at a height of 4 m with a horizontal distance of 55 mfrom Lane 1 of the source road. Each lane has 501 source positions with a uniform interval of 4 m.
Parameter settings are shown in Tables 2 and 3. Meteorological effect is not taken into account.

y

0
10

Lane 1

Lane 2 P
4

Unit of length [m]
1000

45

1000

Figure 4 – Geometry of Case 01: Semi-free field
Unit of length [m]
y
0
10 10

P

Lane 1
Lane 225

Map 11: 8
Map 12: 15

4
1000

1000

10

Figure 5 – Geometry of Case 05: Screening by thick barriers

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Table 2 – Calculation settings (1)Road surface
Representative flow resistivity [kNs/m4]
Air temperature [℃]

DAC 0/11
20 00015

Table 3 – Calculation settings (2)ASJHarmonoise
Vehicle speed [km/h]
Traffic flow [/h]Temperature coefficient [dB/˚C]

Large-sized
Heavy

Vehicle typeMedium-sizedMedium heavy
50
100
0.05

50
0.05

Light
Light
3 000
0.10

The insertion loss by the thick barrier for the ASJ model ΔL IL,ASJ,i and for the Harmonoise model
ΔL IL,HN,i are calculated from L A,i and L A,HN,i , respectively, for Cases 01 and 05, L A,ASJ,i,free ,L A,ASJ,i,barrier , L A,HN,i,free and L A,HN,i,barrier as
ΔLIL,ASJ,i = LA,ASJ,i,barrier − LA,ASJ,i,free,(8)
ΔLIL,HN,i = LA,HN,i,barrier − LA,HN,i,free(9)
3.2 Finite-Difference Time-Domain Simulations
To obtain reference solutions, three-dimensional finite-difference time-domain (FDTD)
simulations are carried out. Figure 6 shows the configuration. Only regions around y = 0 [m] inFigures 4 and 5 are solved, otherwise computational cost becomes too much. Thus the configuration
only contains a single point source for y = 0 [m], S 1 , which is simulated by a Gaussian initial
distribution of the pressure. The size of (h, h b ) in Figure 6 are (4.5, 0) m, (11, 8) m and (18, 15) m forCase 01, Case 05 Map 11 and Map 12, respectively. Other computational parameters are listed inTable 4. The A-weighted SPL L A,ref,i is computed from the one-third-octave-band spectrum of thesolution with the inverse spectrum of the initial Gaussian sound source, the power spectrum of thesource vehicle and the A-weights applied. The frequency range is limited from 50 Hz to 2.5 kHz
because of the computational grid size. The insertion loss by the thick barrier, ΔL IL,ref,i , is calculated
from L A,ref,i for Cases 01 and 05, L A,ref,i,free and L A,ref,i,barrier, respectively, as
ΔLIL,ref,,i = LA,ref ,i,barrier − LA,ref ,i,free(10)zUnit of length [m]

PML

y
x

0.125
S1

P (55, 0.0025, 4)
56

z
y

x
0.5

S1 (0, 0, 0)
20

h

P

hb

Building
25

0.5
10

Figure 6 – Configuration of the FDTD simulations. The y and other axes are not to scale
Table 4 – Computational parameters and values
Parameter
Grid size [m]Time step [s]Number of steps
Half width at half maximum of sound source [m]Speed of sound [m/s]z-coordinates of the source [m]Density of air [kg/m3]

Value
5×10-38×10-631 250
2.5×10-3340
0, 0.3, 0.75
1.205

4. RESULTS
Hereafter, a large-sized vehicle of the ASJ model and a heavy vehicle of the Harmonoise model

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are collectively called a heavy vehicle.
4.1 Source Power Levels
Figure 7 shows ΔL dir and C dirA for each vehicle category. For heavy vehicles, the power level ofthe ASJ model reduces as Ψ increases and is symmetrical to Θ = 0°. The power level of theHarmonoise also reduces as Ψ increases, but is asymmetric to ϕ H = 90° and is stronger for theforward direction. For light vehicles, the directivity is similar for both models in that the power level
reduces as Ψ increases and is symmetrical to Θ = 0° and ϕ H = 90°.

Figure 7 – Source directivity of a (a) heavy and (b) light vehicle of the ASJ and Harmonoise (HN) models
The A-weighted source power level without the source directivity taken into account is shown in
Figure 8. The power levels for the heavy vehicles are nearly identical between the models, whereasthat for the light vehicle of the ASJ model is larger by 2 dB than the Harmonoise model.

Figure 8 – A-weighted source power level without source directivity taken into account
4.2 Insertion Loss and A-weighted SPL
The results presented here except for the final L Aeq are those for Lane 1 because those for bothlanes are similar. The calculation of L Aeq uses the results for both lanes.
Figure 9 presents the insertion losses with respect to the source at y = 0 without the source
directivity taken into account in comparison with the reference solutions. The difference between themodel calculations and the reference solutions are less than 1 dB for Map 11 and approximately 3 dB
for Map 12. Although slightly larger difference with deeper diffraction by the barriers is seen forboth models, the difference for each case is nearly identical between the models and relatively small.

Figure 9 – Insertion losses for Case 05 (a) Map 11 and (b) Map 12 without the source directivity

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Figure 10(A) plots L A,i and L A,HN,i as functions of the y-coordinate of source i for Case 01, Case
05 Map 11 and Map 12 without the source directivity taken into account. The plots can be regarded
as simulated single-vehicle pass-by patterns (the unit patterns) observed at the receiver. For all cases
the plots are symmetrical to y = 0 [m]. For Case 01, a clear geometric attenuation pattern is observed
towards the left and the right ends. For Case 05 Maps 01 and 12, the pattern is not so clear as thegeometric attenuation and the diffraction attenuation cancel each other. Figure 10(B) similarly plots
L A,i and L A,HN,i with the source directivity taken into account. The plots for the heavy vehicle of theHarmonoise model for all cases are characteristic in that they are asymmetrical to y = 0 [m] as
expected from the source directivity shown in Figure 7(a). The L A,i for the large-sized vehicle of the
ASJ model at y = 0 [m] indicated by the (I) label in Figure 10(B) is 2.3 dB smaller than that in Figure10(A). This is because the source power is lost by the application of the source directivity. The plots
for the light vehicles are similar to those for the heavy vehicles.

Figure 10 – LA,i and LA,HN,i for (a), (d) Case 01, (b), (e) Case 05 Map 11, (c), (f) Case 05 Map 12
In all cases plotted in Figure 10, for heavy vehicles the SPLs for the Harmonoise model is larger
than those for the ASJ model. This is because the insertion loss is smaller for the Harmonoise model
as illustrated in Figure 9 whereas the source power levels are nearly identical as indicated in Figure 8.
For light vehicles, the SPL of the ASJ model is generally larger for Case 05 map 11. This is because
the source power level is larger for the ASJ model as illustrated in Figure 8 whereas the insertion loss
is nearly identical as illustrated in Figure 9. On the other hand, for Case 05 Map 12 the SPL for the
ASJ model is generally smaller around y = 0 [m]. This is because the insertion loss of the ASJ modelis larger than the Harmonoise model.
Figure 11 shows L Aeq for each case without and with the source directivity taken into account.
When the source directivity is not taken into account, the L Aeq are nearly identical between bothmodels for Case 01. For Case 05, the L Aeq of the ASJ model is larger for Map 11 but smaller for Map
12 than the Harmonoise model. This follows the observation of light vehicles in Figure 10 as thelight vehicles mostly occupy the traffic volume, as shown in Table 3. The difference between without
and with the source directivity becomes larger as the height of the barrier becomes larger. In all cases,
differences between the models are less than 2 dB.

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Figure 11 – LAeq for (a) Case 01, Case 05 (b) Map 11 and (c) Map 12

5. CONCLUSIONSIn this study, a methodology to derive consistent quantities between the ASJ model and theEuropean Harmonoise model is established. The methodology is applied to thick barrier test casesthat are included in a Harmonoise deliverable. At the same time, finite-difference time-domain
simulations are carried out to obtain reference solutions. A-weighted source power levels between
the two models are found to be larger for the light vehicle of the ASJ model. Comparison between
each model and the reference solutions weighted by each source spectrum agree well for both models.
Single-vehicle pass-by patterns of the Harmonoise model become asymmetrical to y = 0 [m] when
the source directivity is taken into account. The final A-weighted levels obtained by both models
agree within a 2 dB difference. However, the difference in the source directivity and the balance ofthe source power level and the diffraction attenuation may lead to large difference under certain
cases.

ACKNOWLEDGEMENTS
This work was supported by JSPS KAKENHI 16H04462, 17H03350, 18K18897, Grant-in-Aid for
JSPS Fellows 19J13172 and a grant-in-aid contract with The Niigata Engineering Promotion, Inc.

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