The Impact of China's Traffic Noise Spectrum on the Single-Number-

Quantities (SNQs) Evaluation of Airborne Sound Insulation in the

New Era

Yangsheng Cai 1 ; 1. School of Architecture and Urban Planning, Fujian University of Technology, Fuzhou 350118, P,R China; 2. State Key Laboratory of Subtropical Building Science, School of Architecture, South China University of Technology, Guangzhou 510640, P,R China; Zhihui Chen 2 ; 3. School of civil engineering, Fujian University of Technology, Fuzhou 350118, P,R China; Yao Wang 3 ; Xufeng FU 4 ; Zhihong Wu 5 ; Ming Wang 6 ; 4. Cscec Strait Construction and Development Co., Ltd., Fuzhou 350015, P,R China;

ABSTRACT The ISO 717-1 specified the spectrum adaptation terms Ctr, to take into account the spectra of is A- weighted urban traffic noise. It should be noted that the spectra Ctr was adopted from the Nordtest Method NT ACOU 061 (Nordtest, 1987). However, the means of transportation are undergoing great changes, so the characteristics of traffic noises are also changing significantly. Therefore, in order to better resolve the disputes caused by sound insulation and traffic noise in China, it is necessary to explore whether the existing evaluation standards are still applicable to various types of traffic noise. In this paper, the urban traffic noises in China have been measured and analyzed, a new spectrum adaptation terms for airborne sound insulation evaluation is established, and applied to the calculation of sound insulation of several common building components, and its applicability is discussed.

1. INTRODUCTION

In recent years, China's comprehensive transportation system has developed rapidly, which has 1 promoted the growth of the national economy effectively. At the same time, such development also brought many problems to the ecological environment. Traffic noise from main roads, urban elevated roads and high-speed railways will inevitably bring the negative effect to the normal life and personal health of residents along the line. These problems have gradually attracted attentions of scholars [1][2] .

1 cys125@fjut.edu.cn 4 398540811@qq.com

2 Milkyway0120@126.com 5 464192091@qq.com

3 wangyao1@cscec.com 6 415597470@qq.com

iti aac ta. Atal oohesiel 21-24 AUGUST SCOTTISH BENT asoow

The "Annu a l Report on China Environmental Noise Prevention and Control" in recent years showed that the noise complaint rate was high in Chinese urban acoustic environment. The compliance rate was high during the day, but it was low at night, especially in municipalities and capital cities, it was much lower on both sides of the main road, cultural and educational districts and residential area [1] . Such high noise complaint rate may be related to the following three factors: 1) the increasing number of external environmental noise sources, especially low- frequency noise sources; 2) the insufficient sound insulation performance of buildings; 3) SNQs evaluation method of sound insulation performance of building fails to fully reflect the subjective perception.

In order to facilitate the design and evaluation of building sound insulation performance, the weighted sound reduction index can be obtained according to the ISO 717-1:2020, which describes the sound insulation performance of the building in all aspects. In the calculation process, different spectrum adaptations can be made based on the spectrum types and frequency range of the noise source. It should be noted that the traffic noise spectrum adaptation term is the adaptation for the low-frequency noise, the value was adopted from the results of a Nordic test on measuring traffic noise in the 1980s. However, with the changes of the times, the characteristics of noise sources such as mechanical equipment and traffic equipment have undergone great changes, and people's requirements for building performance have also developed from "economical and practical" to "healthy and comfortable". To solve the complaints and disputes caused by these changes in China, simply copying the current international standards will not help at all. Therefore, this paper studied the characteristics of various types of traffic noise in the new era, and compared it with the current standard traffic noise spectrum adaptation curve ( C tr ), which will provide more sufficient basic data reference for the sound insulation design of the buildings along the road.

2. SINGLE NUMBER QUANTITIES

The prediction and measurement results of buildings sound insulation performance were usually expressed as a function of frequencies, which reflects the insulation ability of buildings or building components to different frequencies of noise. Considering that the spectral characteristics of different noise sources have different effects on the actual sound insulation performance of building components, on the basis of using the weighted sound reduction index R w to evaluate the sound insulation performance of components, the pink noise spectrum adaptation term C and the traffic spectrum adaptation term C tr were introduced. The spectrum adaptation curve required to calculate the traffic noise spectrum adaptation term C tr was derived from the traffic noise data measured in Ref. [3]. C and C tr were the A-weighted sound pressure levels of pink noise and traffic noise that were normalized to 0dB, as shown in Figure 1. The application range of the spectrum adaptation terms with respect to these noise sources were shown in Table 1.

Amplititude /dB 105 -10- -204 -30- 1000 Frequency /Hz

Figure 1: Curve of Spectrum adaptation terms Table 1 Spectrum adaptation term for different types of noise source

Spectrum adaptation term C C tr

Living activities (talking, music,

Disco music Urban road traffic Railway traffic at low speeds

radio, TV) children playing Highway road traffic at >80 km/h

Types of noise source

Jet aircraft, large distance

Jet aircraft short distance Factories emitting mainly medium

Aircraft, propeller driven Factories emitting mainly low

and high frequency noise

and medium frequency noise

The current sound insulation performance evaluation method has been used for more than 30 years. Although it has been revised for many times, the evaluation standard of traffic noise still uses the measurement data of Ref. [3] so far.

3. COMPARATIVE ANALYSIS OF TRAFFIC NOISE SPECTRUM

In this section, the relevant data of the spectrum adaptation terms in the current sound insulation performance evaluation method was selected as reference. The spectrum adaptation terms after the weighted averaging of the actual road traffic noise and high speed railway traffic noise were studied, the difference between the results and the pink noise spectral adaptation term C and the road traffic noise spectral adaptation term Ctr was compared respectively, to determine whether the current standard was still applicable to the actual situation of traffic noise in the new era.

3.1. Spectrum Adaptation Terms for Traffic Noise Sources in Current Standards

The spectra adaptation curve for calculating the traffic noise spectrum adaptation term Ctr was derived from the traffic noise data measured in Ref. [3]. All spectra were based on measurements carried out during the years 1982-85 on road traffic, rail traffic and air traffic in the frequency range 50-5000 Hz. The obtained 7 kinds of spectrum adaptation data were represented by A1 to A7, A1 used a mixture of 18 traffic noise measurements from Copenhagen and Gothenburg, the average vehicle speed was about 50 km/h and with about 10% heavy vehicles, A2 adopted traffic noise mixed highway road traffic at 90 km/h. They were both applied to road traffic. Among the 3 spectrum adaptation data A3, A4, and A5, A3 used normal railway traffic at low speeds, A4 represented traffic not belonging to A3 or A5, and A5 used normal railway traffic at high speeds. The remaining two data were applied to air traffic, A6 was aircraft noise representing starting DC- 9s, A7 was aircraft noise representing propeller aircraft.

Figure 2: A-weighted normalized spectrum for A1-A7

T [s) v =] to) p=] Y 9 F gp sepnynidwy T ° 9 ° @ 1000 100 Frequency / Hz

3.2. China`s Traffic Noise Spectrum Adaptation Terms in the New Era

The noise sources data of the main traffic roads in Fuzhou and Hong Kong were measured respectively. The measurement in Fuzhou was chosen to be carried out at different times during the day (06:00~22:00). The measuring point was selected on the one side of the road, 500 meters away from the crossroads, and the height of the measuring point was 1.0 meter. Since the traffic noise is a complex and continuous non-stationary noise that changes with time, therefore, each measurement point was only measured for 3 minutes, thus a total of 4 sets of noise data were obtained. The data obtained in Hong Kong were recorded at 1 meter from the exterior windows of different floors of residential buildings next to the street. The A-weighted normalized spectrum of traffic noise in Fuzhou and Hong Kong was shown in Figure 3.

a) Traffic noise in Fuzhou b) Traffic noise in Hongkong

Figure 3 A-weighted normalized spectrum of traffic noise

In addition to urban traffic noise, since high speed railways were widespread in China, some scholars have also studied the traffic noise problems caused by such widely used high speed railways[4]. The measurement results in this paper were averaged and then compared with the spectrum adaptation terms C , Ctr and high speed railway noise[5], as shown in Figure 4. The sample of road traffic noise spectrum curve in the middle and high frequency bands which above 500Hz was close to the spectrum curve that used to calculate the traffic noise spectrum adaptation term Ctr , in the middle and low frequency bands it was in the middle of the two spectrum adaptation curves, C and Ctr , and it was closer to the spectrum curve that used to calculate the pink noise spectrum adaptation term Ctr.

Amplititude /dB C, tr —i— Cy rz Cy x C, HS — 1-7 1000 Frequency /Hz

Figure 4 Spectrum adaptation Curve Comparison Results

Amplititude/ dB 100 Frequency / Hz 1000 Amplititude/ dB | - 5eF,/ RY A NY 100 Frequency / Hz 1000

3.3. Comparison of Spectrum Adaptation Term for Different Noise Sources

Taking three common exterior wall components as examples, their characteristics were shown in Table 2, and the sound insulation index were shown in the Figure 5.

Table 2 Building exterior wall components Components Areal Density/ kg/m 2 Thickness/mm Reinforced concrete wall 572 240 6mm ordinary glass window 14.6 6 6mm+12mm+6mm ordinary glass window 14.6 24

Figure 5 Sound reduction index of three common components

According to the ISO 717-1, the weighted sound reduction index, spectrum adaptation terms C and Ctr were calculated. And the spectrum adaptation terms were obtained respectively by using the road traffic noise in Fuzhou( Ctr1 ), Hong Kong( Ctr2 ) and the traffic noise of high speed railway( Ctr3 ). The SNQs of different components were shown in Table 2. It can be seen from the table that for different components, SNQs for different spectrum adaptation terms were slightly different. The SNQs of sound insulation were the smallest when using the traffic noise spectrum of the current standard while the SNQs of sound insulation were the biggest when using the pink noise spectrum of the current standard, this was related to the reduction of low-frequency noise emitted by the new era vehicles.

Table 3 Building exterior wall comp one nt s / dB

Components R W C C t r C tr1 C t r2 C tr3 Reinforced concrete wall 56 1 -2 -1 -2 -2 6mm ordinary glass window 31 0 -2 0 -1 -1 6mm+12mm+6mm ordinary glass window 35 0 -5 -1 -3 -2

4. CONCLUSIONS

This paper measured and investigated road traffic noise and high speed railway noise in China in the new era, and compared the results with the current standard of spectrum adaptation terms, the comparison results showed that the curves were quite different. Therefore, it is necessary to carry out further and more systematic research on the existing building sound insulation evaluation methods in combination with the characteristics of noise sources in the new era. The sound quality can be used to help the research for instance. In the next step, we will continue to carry out research in this area to explore the corresponding relationship between traffic noise sound insulation performance evaluation criteria and subjective perception.

Sound reduction index/ dB 705 605 50+ 40 30+ 205 10+ —=— Concrete Wall —e— 6mm single glass windows —4— 6-12-6mm double glasses 100 1000 Frequency / Hz

5. ACKNOWLEDGEMENTS

This work was supported by Opening Project of the State Key Laboratory of Subtropical Building Science, South China University of Technology, China (Grant No. 2019ZB15) and Fujian

Provincial Department of Science &Technology (2021J011071).

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