PROCEEDINGS of the23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

Noise di stri bution change of the ba cksi de urban blocks
dependi ng on the plans of the r oadsi de buil di ngs
Chan-Hoon HAAN1; Yong-Seong KIM2
1,2

Chungbuk National University, Korea

ABSTRACT
It is necessary to investigate the noises of backside blocks which are transmitted through theroadside buildings since many old residences and shops are located in these areas. The noise of thebackside roads is influenced by the following factors such as the height of the roadside buildings, thedistance between the road and the backside streets, distance among adjacent roadside buildings, andthe difference of the adjacent building heights.
The present paper aims to investigate the influence of these factors on the noise of the backside areaof the roads. In order to this, the noise levels were measured in 9 urban blocks of a city. The bothnoise levels on the road and the backside street were measured simultaneously at the designatedpoints of each urban block.
As the results, there is no significant noise reduction due to the width of the buildings in general.
However, in the cases of buildings arranged on one axis beside the road, it was found that theaverage noise reduction was 12dB on the basis of the building height of 4m. Also, it was found thatfor each 4m increase of the building height, noise reduction occurred by 2dB. In general, it wasproved that the noise of the back streets is mainly affected by the lowest height of the roadsidebuildings. It was found that noise is increased by 1dB for each 4m increase of the height difference
between adjacent buildings. Also, it was revealed that for each 0.5m increase in the distance between
roadside building, noise is increased by 1dB.
Finally, the equation for calculating the reduced noise level at the backside area is suggested.
Through the experimental verification, it was revealed that the suggested formula can be a g
ood method for predicting the reduced noise levels at the backside area of an urban block.
Also, it was confirmed that the noise of the backside area is affected by the plan and buildi
ng dimensions of the roadside buildings.
Keywords: Road traffic noise, Urban block, Backside area, Roadside buildings, Noise levels

1. INTRODUCTION
Noises from the main roads reach backside area through the roadside buildings. However, thenoise of the back district is important (1) since many shops and residences are located in these areas.
The noise of the backside roads is affected by the following factors such as the height of the roadsidebuildings, the distance between the road and the side streets, distance among adjacent roadsidebuildings, and the difference of the adjacent building heights. The present paper aims to investigate
the influence of these factors on the noise of the backside area of the main city roads.
Many software programs for predicting noises are easy to present the 3D mapping with theinclusion of many variable, however they are not sufficient for considering the reflection a nd
diffraction effects of the noises in the real environment. That is why there is not little difference
between the predicted noises and real measured noises in the complex city where many buildings areconcentrated in a city block.

12chhaan@cbnu.ac.kr
zing_kys@naver.com

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2. MEASUREMENT OF THE ROAD TRAFFIC NOISES
2.1 Target Urban Blocks Investigated
The urban blocks are built in lattice type by the intersection of the roads. In urban blocks, there arevarious types of buildings with different shapes so that they may have their own characteristics intransmitting the noises through them to backside area. Also, there are many spaces among buildings
which can be the passages of noise transmission to the backside area. (2)In order to investigate the influence of the roadside buildings on the noise of backside area, 9 blocks
were selected in a busy city in Korea. All the blocks have traffic noise levels of more than 10dB in
comparison with the background noise levels. Table 1 shows the road width, speed limit, and traffic
volume of each target areas investigated. The geometric and space information of roadside buildings
was obtained through the Spatial Open Platform of the National Geographic Information Institute (3,4).
Traffic volumes were investigated by the camera for 5 minutes.
Table 1 – Road width and traffic volume in the  target urban blocks.
Targetblocks

Speed limit

Road widthABCDEFGHI

50 km/h
50 km/h
50 km/h
60 km/h
50 km/h
50 km/h
30 km/h
60 km/h
60 km/h21.8 m15 m
15.4 m15 m
20.1 m13.2 m
13 m
34 m
34.2 mTraffic volume(for 5 min)lightHeavyvehicle
vehicles14222105
1298
10115
23112
1767
5108
16358
31342
21

2.2 Road Traffic Noise Measurements
Noise measurements were carried out during the daytime at the 9 blocks. The noise levels on theboth roadside road and backside streets were measured simultaneously. Leq for 10 seconds weremeasured during the vehicles’ driving. Noises were measured at the several points including the centerand end points of buildings and the point in between adjacent buildings. Microphones were place 1maway from the outer wall of buildings with height of 1.5m from the floor. Fig. 1 displays the noise
measurement points of each block and the division of the backside area (X and Y).

Figure 1 – Location of noise measurement positions and the division of backside areas (X and Y)

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

2.3 Results of the Noise Measurements
As a result, the roadside noise levels of the 9 urban blocks were from 67.0dB to 75.6dB in average,
meanwhile backside noise levels were from 49.3 dB to 57.2dB. Table 2 lists the average noise levels ofeach roadside and backside streets of the 9 blocks. It was examined that roadside noise levels exceed
the noise criteria of 65dB in all the blocks, while backside noise levels exceed the noise criteria of
55dB in A,C,D,E,H blocks. The maximum noise reduction at the backside area was occurred at I blockwith 19.2dB.
Table 2 – Measured average noise levels of the roadside and backside area. dB(A)TargetblockABCDEFGHIAverageRoadside noise[dB(A)]71.4
67.0
71.0
69.6
71.4
69.0
67.1
71.9
71.8
70.0

Backside noise[dB(A)]
56.0
53.0
55.7
55.9
56.6
52.7
49.3
55.5
52.6
54.1

Noise difference[dB(A)]
15.4
14.0
15.3
13.7
14.8
16.3
17.8
16.4
19.2
15.9

3. NOISES ANALYSIS IN THE BACKSIDE BLOCKS
3.1 Noise Analyses
Fig. 2 shows the definition of the dimensions of the roadside building which affect the noise levels
at the backside area. Through the noise analysis, it was shown that noise levels at the backside region(X) of buildings and the region in between buildings (Y) are different. Noise levels at the center pointand end points of the backside region (X) of building are also different since noises are diffracted at theedge of the buildings. Nevertheless, the average noise levels of X are used for analysis.

Figure 2 – Roadside building dimensions affecting the noise level of the backside area.


It was analyzed that noise levels in X region are being decreased with increasing building height.
Fig. 3 displays the average reduced noise levels at X region according to the height of the roadsidebuildings. It was found that for each 4m increase of the building height, noise reduction occurred by
2dB in average. Table 3 shows the round-off noise levels deduced by the roadside building height.

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



Figure 3 – Reduced noise levels at the backside area (X) by the building height (h).
Table 3 – Reduced noise levels in the backside area (X) by the building height (h).
Building
4m
8m
12 m
16 m
20 m
22 m
height (h)Reducednoise level 12 dB(A) 14 dB(A) 16 dB(A) 18 dB(A) 20 dB(A) 22 dB(A)(H)
The noise levels in Y region are different with the levels in X region. It was analyzed that noiselevels in Y region are affected by three factors of the roadside buildings.
1) Height of the adjacent buildings (h)2) Distance between adjacent buildings (d)3) Difference of building height of adjacent buildings (ȟ )First, in case of that adjacent buildings have same height, the noise levels in Y region are also being
decreased with increasing building height. Fig. 4 displays the average reduced noise levels at Y region
according to the height of the roadside buildings when adjacent buildings are separated by 1.5m. It was
found that for each 4m increase of the building height, noise reduction occurred by 3dB in average.
This value is bigger than the reduced noise level at P region while the absolute values at Y region isstill greater than those of P region.

Figure 4 – Reduced noise levels at the backside area (Y), when the adjacent buildings have same height.

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Secondly, when adjacent buildings have same height, the noise levels in Y region are increased bythe separation distance between two adjacent buildings. Fig. 5 displays the average reduced noiselevels at Y region according to the distance between two adjacent buildings with same height of 12m.
It was revealed that for each 0.5m increase of the separation distance (d), noise increased by 1dB inaverage. This value is bigger than the reduced noise level at P region while the absolute values at Y
region is still greater than those of X region.

Figure 5 – Reduced noise levels at the backside area (Y) depending on the separation distance (d).
In order to find the variation of the noise levels in Y region affected by the buildings height (h) andthe separation distance (d), the difference of the reduced noise levels at the X and Y region by those
two factors are listed in Table 4.


Table 4 – Difference of reduced noise levels (D) at the backside area X and Y by
two factors; separation distance(d) and the height (h) of adjacent buildings [dB(A)]
Adjacent two buildings height (h)Items

Separation
distance (d)

4m

8m

12 m

16 m

20 m

0.5 m

0123

41m-1012

3

1.5 m

-2-10

1

22m-3-2-10

1

2.5 m

-4-3-2-10Lastly, when adjacent buildings have same separation distance, the noise levels in Y region areincreased by the difference of the building height ( ȟ) of the two adjacent buildings. Fig. 6 displays
the average reduced noise levels at Y region when one building with 4m height is adjacent withdifferent heights of buildings. It was found that for each 4m increase of the difference of adjacentbuilding height ( ȟ), noise increased by 1dB in average. Table 5 shows the averaged reduced noiselevels at Y region depending on the height difference of adjacent buildings. It was also known that thenoise levels in Y region are determined by the lower height of building when two adjacent buildings
have different heights.

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Figure 6 – Reduced noise levels at the Y region by the height difference (∆h) of the adjacentbuildings, when the lower building is 4 m high with the separation distance of 1.5 m.

Table 5 – Reduced noise levels at the backside area (Y) depending onthe height difference (Ѭh) of the adjacent two buildings.
Building heightdifference (∆h)
Reduced noise level(HD)

4m8m

12 m

-1 dB(A)-2 dB(A)-3 dB(A)

3.2 Noise Prediction Formula suggested
Through the noise analysis of the three factors which affect the noise levels at the backside area, theequation for calculating the reduced noise level at the backside area is suggested as follow; (5)5 1  + 㸩' 㸩+ ' >I% $ @ where, RN : Reduced noise level at the Y region [dB(A)]H : Reduced noise level at the X region by the building height (h) (refer to Table 4)
D : Reduced noise level at the Y region by separation distance of building (d) (refer to Table 5)
HD : Reduced noise level at the Y region by the building height difference ( ȟ) (refer to Table 6)
H and D are calculated on the basis of the lower height (h) of the two adjacent buildings. Since
there are no buildings in front of Y region, reduced noise level (H) at the X region by the buildingheight was used for calculation of the reduced noise level at Y region. It is also because there arealmost same value of the reduced noise level at the both X & Y regions taking into account the factorof building height only.

4. VERIFICATION OF THE SUGGESTED FORMULA
In order to verify the suggested equation, two new blocks (P & Q blocks) were selected to beinvestigated besides 9 blocks. These two blocks have buildings with different height (h), separation
distance (d), building t height difference ( ȟ) in comparison with the existing 9 blocks. The reduced
noise level at the backside area of these two blocks were calculated using the suggested equation. Also,noise levels were measured in the same way at the P & Q blocks. Lastly, the measured level difference
was compared with the predicted level using this equation.
Table 6 shows the information of the road traffic conditions of P & Q blocks. Table 7 shows thebuilding heights (h) and the separation distance (d) of the four consecutive buildings in each P & Q
blocks.

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Table 6 – Road traffic conditions of P and Q blocks
traffic volume(for 5 min)LightHeavyvehicle
vehicles

BlockSpeedlimit

RoadwidthP

60 km/h

21 m

158

30Q

30 km/h9m

65

8Table 7 – Building height and separation distance of the consecutive buildings in P & Q blocks.
BlocksBuildingheight (h)

PQ

P1

P2

P3

P4

Q1

Q2

Q3

Q4

12.3 m16.4 m21.8 m14.3 m

6 m

4 m

8 m

8 m

Separation
distance (d)

P1-P2

P2-P3

P3-P4

Q1-Q2

Q2-Q3

Q3-Q4

1 m

0.5 m

1.1 m

2.2 m

2.1 m

1.86 mTable 8 and Table 9 show the predicted and measured value of reduced noise levels at the X and Yregions of the P & Q blocks respectively. In Tables 8 and 9, it was revealed that the number of error ofthe predicted values of the reduced noise levels at the backside area is within 1 dB at the both X and Y
regions which is smaller than the 3 dB JND of the noise levels.
Table 8 – Comparison of the reduced noise levels at the X regionof P & Q blocks both predicted (H) and measured values [dB(A)]Predicted value(H)

Measured noise
difference

Number of error

P1

1615.90.1

P21818.2

0.2

P3

2121.40.4

P4

17

16.1

0.9

aver.

18

17.9

0.4

Q1

1313.20.2

Q21212.2

0.2

Q3

14

14.5

0.5

Q4

1414.6

0.6

aver.

13.25

13.63

0.38

BlockPQ4397

Table 9 – Comparison of the reduced noise levels at the Y regionof P & Q blocks both predicted (RN) and measured values [dB(A)]Predicted value(RN)

Measured noise
difference

Number of error

P1-P2

1617

1.0

P2-P3

1919.8

0.8

P3-P4

16.5

15.9

0.6

aver.

17.2

17.6

0.8

Q1-Q288.8

0.8

Q2-Q388.3

0.3

Q3-Q4

12

11.7

0.3

aver.

9.3

9.6

0.47

BlocksPQ

5. CONCLUSIONSThe present paper aims to predict the noise levels at the backside area using the only information of
the roadside buildings. Through the results and the analyses of the study, it was revealed that thesuggested formula can be a good method for predicting the reduced noise levels at the backside area ofan urban block. Also, it was confirmed that the noise of the backside area is affected by the plan andbuilding dimensions of the roadside buildings.

REFERENCES
1. Lee J. W. Prediction and analysis on the road traffic noise attenuation according to geometric conditionsof the building nearby the roads, Master Thesis, University of Seoul, Korea 2009.
2. Jang C. M. Statistical analysis of the relationships between measured road-traffic noise level and urban
characteristics, Master Thesis, University of Seoul, Korea 2017.
3. National Geographic Information Institute, Spatial Information Open Platform,
http://www.vworld.kr/dev/v4api.do
4. National Geographic Information Institute, http://map.ngii.go.kr/mn/mainPage.do/ 2015.
5. Kim Y. S. Analysis on the correlation of noise in the backside urban blocks with the plan of the roadsidebuildings, Master Thesis, Chungbuk National University, Korea 2019.

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