Modeling the impact of traffic noise: analysis of lightning geometry and its contribution to direct, specular, and diffuse path propagation Dayane Cristina Lima Estercio 1 State University of Campinas, UNICAMP, Saturnino de Brito Street, 224, 13083-889 - University City, Campinas - SP, Brazil. Paulo Fernando Soares 2 State University of Maringá, UEM, Avenue, 5790 - University Garden, 87020 900 - Maringá - PR, Brazil.

ABSTRACT The evaluation of urban noise is an important tool in noise control. From existing sources of noise, vehicular traffic is considered the main cause of discomfort in the population. The intensity of the noise that reaches the receiver depends on the level of sound power emitted by the source and the attenuation that occurred in the propagation medium. The analysis of the dispersion of rays in dif- ferent urban geometries allows the evaluation of parameters that influence the trajectory of noise. The objective of this work is to analyze the contribution of the energy fraction of each path in global noise in different urban configurations, to contribute to the analysis and adoption of mitigating measures. For this, the mathematical model of prediction of noise levels was adopted, which calcu- lates the direct paths and specular (source-image method) and diffuse (radiosity method) paths. The study was applied in two sectors of the city of Maringá, Brazil. In total, 73200 paths were evaluated in 2928 readings of source positions in 54 measured points. The results showed the part of contribu- tion that each path represents in the acoustic field, and the sound decay caused by obstacles, urban geometry, distance and material properties.

1. INTRODUCTION

The assessment of urban noise has become an important tool, as it helps in the application of inspection and control measures. Research shows that exposure to noise can lead to health problems for people. The effects on the population's health and quality of life are related to the exposure time, intensity and frequency of the noise emitted by sound sources [1,2].

One of the forms of noise assessment used in research and studies are prediction models. These models apply mathematical algorithms or software that assist in the identification of critical points, assessment of population exposure and simulation of mitigation measures in noise maps [3]. Prediction models use parameters such as: number of vehicles, percentage of heavy vehicles, sound power, average speed, source-receiver distance, road dimensions, the size of the buildings, among others [4-8]. Other models incorporate parameters such as sound wave geometry, incorporating or analysis of specular reflections (image source method) and/or the effects of scattering and diffusion (radiosity method) [9-16].

1 esterciodayane@gmail.com 2 pfsoares@uem.br

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The object of study of the research are the bus stop, these are important urban equipment and are used daily by the population throughout the day. The objective of this work is to analyze the contri- bution of the energy fraction of each path in global noise in different urban configurations, to con- tribute to the analysis and adoption of mitigating measures. 2. METHODOLOGY

The methodology of the work consists in the analysis of the propagation of sound rays. For this, the work was divided into in loco monitoring, modeling of the analyzed stretch, through the applica- tion of the predictive model. Analysis of parameters that influence sound propagation. And statistical calculations to evaluate the contribution of specular and diffuse reflection.

2.1. Case study

The study was applied in the city of Maringá, in Paraná state, Brazil, as shown in Figure 1. Two sections with different urban configurations were analyzed. In each stretch, as shown in Figure 2 and 3, features thirty meters wide and one hundred meters long.

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Figure 1: Case study location.

Section 01 mm Section 02

Figure 2: Stretch 1, Kakogawa Avenue.

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Figure 3: Stretch 2, Joubert de Carvalho street. Stretch 01 features a six-lane, two-lane route for buses. Five bus stops were measured, in each two points were measured, the first point at the height of the user standing and the second at the time of the seated user. Stretch 02 features a 2-lane, mixed-use route.

2.2. Mathematical model

Tae

The model adopted in the research is the one developed by Estercio and Soares [17] who estimates the levels of noise emitted by the noise of vehicular traffic that arrive in the users of public transport in bus points. The model calculates the noise based on direct, specular and diffuse sound rays as shown in Equations 1, 2, 3, 4, 5. For finalizing, the summation of the sound rays and the correction coefficient C are calculated (Equation 6).

𝐼 𝑑 = 𝑊 𝑒 + 10𝑙𝑜𝑔 ቆ Ω 4Π𝑑 𝑇

2 ቇ+ 𝑒 ൬ 4 −𝜓𝑑 𝑇

൰ (1)

10

𝐼 𝑒 = 𝑊 𝑒 + 10𝑙𝑜𝑔 ቆ Ω 4Π𝑑 𝑇

2 ቇ+ 𝑒 ൬ 4 −𝜓𝑑 𝑇

(2)

൰෍ൣ൫1 −ሺ𝛼 𝛼 + 𝜁 𝛼 ሻ൯൧

𝛼=1

𝐼 1 = 𝑊 𝑝 + 10𝑙𝑜𝑔 ቆ Ω 4Π𝑑 𝑝𝑟 2 ቇ+ 𝑒 ቆ 4 −𝜓𝑑 𝑝𝑟

ቇ (3)

Comme

𝑊 p = 𝑊 𝑒 + 10𝑙𝑜𝑔 ቆ Ω 4Π𝑑 𝑒𝑝 2 ቇ+ 𝑒 ቆ 4 −𝜓𝑑 𝑒𝑝

ቇ𝜁 𝑝 𝐴 𝑝 (4)

Ω𝐹𝐹 𝑗𝑖 𝑒 −𝜓𝑑 𝑖𝑗

2 ቇ+ 𝑒 ቆ 4 −𝜓𝑑 𝑗𝑟

ቇ (5)

𝐼 2 = 𝑊 𝑝 + 10𝑙𝑜𝑔 ቆ

4Π𝑑 𝑗𝑟

𝐶= 6 ൬1 + % ℎ𝑒𝑎𝑣𝑦

100 ൰ (6)

Where W e is Sound power of the source, W p is the sound power of the stretch Ω is the factor of directionality, d T is the distance between the source and receiver, ψ is the attenuation of the air, α α is the absorption coefficient and 𝜁 α is the spreading coefficient, A p is the area of the stretch, FF is the form factor and ψ is the air attenuation and % heavy is the percentage of heavy vehicles.

2.3. The variables adopted

The variables adopted in the study were: sound power level of the source, number and type of vehicles, percentage of heavy vehicles, distance from source to receiver, materials ownership (the absorption coefficient, the scattering coefficient), dimensions of the road and surroundings, obstacles (vegetation and structure of the bus stop). To analyze the contribution of each path, statistical analysis was performed. The values were calculated in third octave bands. 3. RESULTS AND DISCUSSION

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3.1 Path

The analysis of sound rays allows evaluating the contribution in the overall result. In the research, the sound rays that: collided with obstacles (trees or the structure of bus stops) and those that passed the limit of the evaluated section were discarded. The research evaluated a set of predefined reflec- tions, to show the possible contributions that each presents in the overall result (see Figure 4).

Figure 4: Stretch profile with calculated radii. The assessment was performed for the exposure of sound levels for the user sitting and standing. The analysis of each radius separately shows the sound decay along the pathway. The maximum decay of each path, for the user standing as shown in Figure 5, was 29 dB in stretch 1, 32 dB in stretch

= Direct = Specular (Building) = Specular (Stree) — Diffuse (IST Order ~Stop bus) = Specular (Stop bus) — Diffuse (2ST Order - Street and Building)

2, for the direct path. For the specular path 1 was 30 dB in stretch 1 and 32 in stretch 2. This path evaluates the sound reflection on the road, sidewalk or in the central flowerbed. On the specular path 2, it analyzes the reflection surface of the back of the bus stop. The levels obtained were 31 dB for section 1 and 2. The specular path 3 evaluated the reflections that occurred on the facades of the buildings. The values presented were 16 dB in section 1 and 23 in stretch 2.

For the diffuse path 1, the reflections on the coverage of the bus stop were evaluated. Due to the type of bus stop coverage were calculated at the two source positions closest to each bus stop. Thus, in section 1, the calculated source positions were 24 and 25 at bus stop 1, 25 and 26 at bus stop 2 and 3, 33 and 34 at bus stop 4, 34 and 35 at bus stop 5. In stretch 2, the calculated source positions were, 3 and 4, to bus stop 1, 13 and 14 to bus stop 2, 18 and 19 to bus stop 3, 26 and 27, to bus stop 4 and 38 and 39 to bus stop 5. In this path the decay was about 5 dB and 2 dB, in sections 1 and 2, respec- tively. The last specular path 3

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Figure 5: Noise intensity of sound paths calculated along Kakogawa Avenue.

SsBssssseS CsBsSsZzss sBsssSsss SsysssIsss Csysssssess SeSSSESSSS= NIMES ili NEN RORANISNSRARARAAASERARS: wl FISTSES TART ii ii FESS: Bus stop 01 stop 2 MRRASS hicdadl [ia ~CU ce

For the sitting user, the variation of sound levels in the direct path, as shown in Figure 6, were 28 dB, for stretch 1 and 33 dB in stretch 2. In this position the decay was higher compared to the standing user. In the specular path 1 the values were 28 dB and 33 dB, for stretches 1 and 2. In the specular path 2 the values were, 30 dB and 34 dB respectively. In the specular path 3 the variation was 14 dB for stretch 1 and 26 in stretch 2. The analysis of diffuse pathways showed a decay of 2 dB in both stretches. The diffuse 2 the loss of energy along the path was greater, because it analyzes more than one reflection. The calculated trajectory analyzes the reflection that occurs on the ground (the road, the central flowerbed or the grounded) and the reflection in the surrounding buildings. In this path the decay was 35 dB for stretch 1 and 51 dB in stretch 2. The sound decay on this path was about 30% more than the user standing.

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Figure 6: Noise intensity of sound paths calculated along Joubert de Carvalho street.

‘du Pu SSSSESEEE: i SEERE ANAT REEASS Bus stop 2 0 0 20] 10) o SUSESEBSE SAAN N LEAD RE AANANAR RARE AREDAATTIT EGET SS AAAAMARO ARES 20 Ht Bus stop 3 0 Il HH ll ENE ORENTSNENRRANAEASS? 2: ll | tN Il =a ° susseesEee=' RRRARAASAAR RASS UIT OSES SRR AAA ARRAS 90 oe Bus stop 5 70 0 os nM SUSSSSSSSSANIANLNE ARAANAGSHARR ARNT MERARS TTI TET FORT, ily sca ~=CMe =< as aan Sona

The analysis of the paths shows that the direct path presents values that most contribute to the overall result. Followed by the specular paths. And finally, the diffuse paths. 3.1 Overall result

The results calculated in the model presented values close to the measured in loco , as shown in Table 1. The levels showed a maximum variation of 0.9 dB for standing users and 1.4 dB for seated users. Licintra and Menoli [18] describe that the difference should be at most 4.6 dB me standard deviation.

Table 1: Comparison of the results obtained with the developed model and the data measured.

STRETCH 01 STRETCH 02 L Aeq, 5min - dB L Aeq, 5min - dB Tuesday Tuesday Wednesday Thursday Tuesday Wednesday

Bus stop User Model

Standing Developed 68.6 67 68.6 68.2 68.1 69.4 Measurements 68.4 67 67.7 68.9 67.6 68

01

Sitting Developed 64.2 68.9 63 68.6 69.3 69.4 Measurements 64.7 69.7 62.2 68.3 69.6 69.1

Standing Developed 64.3 66.4 67.4 68.6 69.8 70 Measurements 64.4 66.4 67.7 68.4 70 71

02

Sitting Developed 63.3 69.1 67.1 71.9 69.3 71 Measurements 63.9 70 67.6 71.4 69.3 70.9

Standing Developed 70.8 67.3 64.1 64.9 67.4 68.2 Measurements 70.5 67.1 65.9 64.6 67.2 67.3

03

Sitting Developed 67.4 67.1 65.6 69.3 66.3 68.2 Measurements 68 67.6 66.2 68.6 66.6 68.2

Standing Developed 71.8 69.6 74.3 68.6 67.4 64.8 Measurements 71.6 69.4 74.4 68.7 67.7 66.1

04

Sitting Developed 66.7 71.9 64.1 64.9 71.1 64.8 Measurements 66.9 71.3 64.4 64.4 71.4 65.4

Standing Developed 65.5 72.1 66.5 66.3 68.3 69.9 Measurements 65.4 72.2 66.8 66.1 69.0 69.7

05

Sitting Developed 67.5 69.2 71.5 75.6 67.3 69.9 Measurements 67.7 69.3 71.5 74.9 66.5 70.2

The similarity between the model and the data measured in loco were higher than 95%. The values were higher than the limits described by local legislation. 4. CONCLUSIONS

It is concluded with the research that the evaluation of the separate paths allowed the analysis of the energy fraction that each path in the overall result. It also made it possible to study the sound decay that each path suffers along the road. The calculation in different surfaces and at different points allows analyzing the properties of the materials based on the coefficient of scattering and absorption, and shows what the possible critical points, allowing the study of mitigation measures in certain areas.

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5. ACKNOWLEDGEMENTS

The present work was carried out with the support of the Coordination of Improvement of Higher Education Personnel-Brazil (CAPES) and, for participation in the Inter Noise Congress 2021, ob- tained the support of the "Latin American Young Professional-LAYP 2021". The research was de- veloped at the State University of Maringá, 6. REFERENCES

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