Research on indoor noise evaluation and optimal design of university

library——Taking the library of Wushan campus of South China

University of Technology as an example

Yang Zhang 1* Department of Architecture, School of Architecture, South China University of Technology 381 Wushan Road, Tianhe District, Guangzhou, Guangdong, China Hongwei Wang 2 Department of Architecture, School of Architecture, South China University of Technology 381 Wushan Road, Tianhe District, Guangzhou, Guangdong, China Chenxi Yang 3 Department of Architecture, School of Architecture, South China University of Technology 381 Wushan Road, Tianhe District, Guangzhou, Guangdong, China

ABSTRAT Due to the special use requirements of university libraries, the requirements for indoor acoustic environment quality are relatively high. By investigating the layout and structural design of the library on the Wushan campus of South China University of Technology, distributing questionnaires to users and conducting on-site monitoring, fiunally finded out the noise problems of the library, such as the sound of connecting the upper and lower floors, noise of friction with the ground when walking, keyboard tapping, moving seats, flipping and rummaging books, air conditioning and ventilation equipments, near the toilet and the elevator was noisy, moreover, the actual measurement of the sound level meter showed that the noise of reading area exceeded 40dB ( JGJ 38-2015 Code for Design of Library Buildings stipulates that the noise limit of the library reading area is 40dB). Based on the above problems, the corresponding optimization measures were put forward, in order to provide technical references for the design and transformation of the acoustic environment of other domestic university libraries. Key words: university libraries; South China University of Technology; on-site monitoring; acoustic environment 1. INTRODUCTION

At present, with the rapid development of higher education all over the world, the scale of schools is getting larger and larger, and the quality of people's life is improving, so higher requirements are put forward for school libraries.As the center of university learning and education, university library plays an important role, so it is vital to create a good learning, reading and working environment. With the increase of the number of users, how to control the noise of library

1 1554067014@qq.com (Y. Zhang).

2 wanghw@scut.edu.cn (H. Wang).

is particularly critical.In recent years, some scholars have carried out some researches on the acoustic environment of university libraries, but generally the researches are not deep and extensive enough.Ji Xianrong analyzed the acoustic environment, architectural characteristics and individual factors of the indoor space of several university libraries in China.The results showed that the flow of people had a significant effect on sound pressure level and loudness.At the same time, time factor, space factor and the cross effect of two factors also had significant influence on sound pressure level and loudness[1].Taking the libraries of Yingxi campus and Huyu Campus of Taiyuan University of Technology as examples, Wang Zhenjiang concluded that most people would be affected by various noises in study and work through subjective questionnaire survey and objective field measurement analysis. Most people thought that the planning location of the library in the campus, the quiet zoning of the library building function and the sound insulation and absorption of the indoor space are the main reasons that affect the sound environment quality of the university library.At the same time, a large number of outdoor measurement points exceeded the standard limit, while indoor, self-study areas, traffic spaces (such as lobbies and corridors) and other places had higher noise values than the national standard limit.Finally, some methods and measures that could be used to control the acoustic environment of university libraries were summarized [2].Gong Chengchao according to the survey data of a few colleges and universities libraries of comparative analysis in Guangzhou University Town, it was concluded that the main factor affecting the noise environment of open shelf reading space of university libraries was indoor noise, among which the most prominent ones were the noise echo of atrium space, toilet and machine room equipment near reading area, artificial noise such as moving tables and chairs and computer typing;outdoor site selection also had some noise, but the overall impact was not significant, the main noise sources were the main entrance square of the library, the motor vehicle road near the library and the playground, among which the playground noise had a relatively large impact[3].

Although the above research had done measured analysis and subjective evaluation on the indoor and outdoor space of library, it was relatively not detailed enough and the testing instruments used were not accurate enough, so there is still a lot of room for improvement. In this paper, the sound environment was measured by using the internationally advanced B&K2270 sound level meter in Wushan Campus library of South China University of Technology and subjective evaluation of the accoustic environment of the library were couducted by users, and comprehensively analysed the factors influencing library sound environment and people's subjective feeling, finally put forward the practical measures to solve the problem of noise, and in order to provide reference for dealing with the acoustic environment of university libraries in South China. 2. RESEARCH METHODS 2.1. Research object

The library of Wushan Campus of South China University of Technology was selected as the research object in this paper. The library is ingeniously connected with the old and new libraries. It is simple, elegant and solemn, with a building of four floors, a total construction area of 21,000 square meters and more than 2,300 seats (FIG. 1). The library is close to the south gate of the university, close to the swimming pool and gymnasium on the east side, and facing the road on the west and north sides (FIG. 2), with traffic noise.The first floor of the library is mainly for service, for teachers and students to borrow and return books, consultation, inquiry and other services, the north building is set up office and study area;The second and third floors are open lending spaces. The north and south buildings are connected by a corridor, where self-service storage and service areas are set up.The fourth floor is a diversified learning and research space, which is a separate small space for group discussion (FIG. 3).

2.2. Research methods 2.2.1. Sound pressure level measurement method

The international advanced B&K2270 sound level meter was selected as the test instrument. The measurement period was from 19:00 to 22:00 at night, which was the time when the library had the largest number of people.Each floor was equipped with measuring points, focusing on monitoring the entrance hall, toilet, elevator, equipment room, control room and air outlet of ventilation duct, as shown in Figure 4-7.When measuring, the sound level meter was 1.5m above the ground and more than 1.2m away from the wall and other reflective surfaces, and the test time at each point was 10 minutes.

Figure 1: Exterior view of the library Figure 2: Map of Wushan Campus Library

Figure 3: Library interior 2.2.2. Subjective questionnaire design

The questionnaire design focused on the subjective feelings of teachers and students about noise, which noise disturbed users more, what kind of acoustic environment they liked to study in, and the influence of outdoor noise.Through the form of network questionnaire, in order to fast and efficient statistic analysis, finally collected a total of 107 questionnaires, and used origin software for statistical data analyed.

Figure 4: Library 1F measuring point Figure 5: Library 2F measuring point

Figure 6: Library 3F measuring point Figure 7: Library 4F measuring point 3. RESEARCH RESULTS 3.1 Measured results

According to JGJ 38-2015 Code for Design of Library Buildings ， the limit value of sound pressure level in quiet area (reading area, research room, etc.) of library is 40dB, that in quieter area (electronic reading room, office, audio-visual room, etc.) is 45dB, and that in noisy area (reader rest area, toilet, hallway, corridor, etc.) is 50dB.The measurement results of all points were shown in FIG. 8. Through statistical analysis of the measurement points of each floor, it was found that the noise level in reading area was all over 40dB (FIG. 9), and the maximum sound pressure level was at measurement point No. 9 (the outlet of air duct in the north of the 2nd floor). Field observation found that the outlet pipe vibration was strong and the noise was large. The minimum sound pressure level in reading area was located at No. 19 (east of the learning and research space on the 4th floor). According to the survey, it was close to the equipment room and there were continuous ringing bells in the room.Through statistical analysis of the data of each measurement point in reading area, it was found that the average sound pressure level was 54.9dB, which exceeded the standard limit by 14.9dB and surpassed the standard limit seriously. In addition, during the investigation, it was found that in other reading areas the sound of connecting the upper and lower floors, the sound of rubbing against the ground when walking, the sound of tapping the keyboard, the sound of moving the seat, and the sound of flipping books were also louder, which had a bad influence on users.

The analysis of the public area showed that the maximum SPL was 51.4dB(FIG. 10) at point 5 (elevator entrance on the first floor), which was accompanied by the sound of elevator door opening and closing and the broadcasting sound of the nearby seat reservation machine. The lowest SPL was

located at point 6, and the SPL was relatively small at the stairway on the second floor.The average sound pressure level of each point in the public area was 49.0dB, which basically met the requirements of the specification.In general, the sound environment of the library was poor, which made teachers and students feel bad.

LAcq so. 20. ELA S68 F (eaniiesianih pied

Figure 9 : Statistical diagram of sound pressure level of measuring points in reading

Figure 8: Statistical diagram of sound pressure

level at measuring points of each layer

area of each floor

Figure 8:Statistical diagram of sound pressure level of measuring points in public area of each floor 3.2.Questionnaire analysis

Through sorting out the questionnaire, it was found that 61.11% of the users felt that the library was noisy, only 5.56% of teachers and students felt that the library was especially quiet (FIG.11), and 66.67% of the users felt that they could not study, and 22.22% felt that the library needed to be reconstructed to use it(FIG. 12).At the same time, 38.89% of the users felt that the vibration at the outlet of the air duct was strong(FIG. 13), which had a great impact on learning. Some of them also felt that the noise near the equipment room, the ceiling pipe, the elevator entrance, the entrance hall, the control room and the toilet also had an impact.According to the statistical analysis of what kind of sound environment teachers and students would like to study in, 55.56% of them liked to study in a very quiet environment, 33.33% and 11.11% of users enjoyed studying in a natural sound (such as birds, insects, water) and pleasant music environment respectively(FIG. 14).Therefore, natural sound and musical sound with low sound pressure level could be appropriately introduced in the reconstruction of library acoustic environment to improve people's learning efficiency.Finally, the influence of outdoor noise was analyzed, and it was concluded that most users thought the influence of aircraft noise (27.78%), infrastructure construction noise (22.22%), motor vehicle noise (22.22%) and outdoor pedestrian noise (22.22%) was great(FIG. 15), and measures should be taken to reduce

@evi (Biante

the impact of noise.

5.56%

Figure 10 Statistical diagram of

Figure 9 Statistical diagram of

acoustic environment feeling

learning experience

5.56% 556% Ss6% 388996 raroy 160m 16.67%

Figure 11 Statistical diagram of noise influence at different positions

Figure 12: Statistical diagram of acoustic

environment preferences

Figure 13: Statistical diagram of outdoor noise influence 4. SUMMARY AND SUGGESTIONS

5.56% 16.67% 16.67% Noisy [EEG Quiet [JN] Ondinary FS Very quiet

Taking the library of Wushan Campus of South China University of Technology as the research object, this study measured the actual noise situation of each reading area and public area during the main use period, and conducted a subjective feeling survey to understand users' satisfaction with the library's acoustic environment, specific interference factors and preferences of the acoustic environment.The following conclusions were drawn from the study:

1) The measured results showed that the noise in reading area was rather high. Due to its proximity to the wind outlet, equipment room and control room, the average sound pressure level

was 54.9dB, which exceeded the standard seriously. In addition, in other reading areas the sound of connecting the upper and lower floors, the sound of rubbing against the ground when walking, the sound of tapping the keyboard, the sound of moving the seat, and the sound of flipping books were also louder, which had a bad influence on users. The noise in public area was relatively less, but also close to the standard limit.

2) From the subjective questionnaire analysis, most users felt that the library was noisy, and 66.67% of teachers and students felt that they could not study.People mainly felt the air conditioning duct exit, equipment room, ceiling pipe flow sound, by the elevator, entrance hall, control room, toilet noise was more serious.At the same time, 33.33% and 11.11% of the users preferred to study in the environment with natural sounds (such as birds, insects, water) and pleasant music respectively.In terms of outdoor noise, people mainly felt the impact of aircraft noise, infrastructure construction noise, motor vehicle noise and outdoor pedestrian noise had a greater impact.

3) As for the improvement of the acoustic environment of the library, glass fiber sound- absorbing cotton and sound-insulating cotton blankets could be wrapped around the air- conditioning pipes, sound-absorbing wall panels and ceilings could be added to the walls and ceilings of the equipment room and control room, and carpets should be laid in the entrance hall. Notice ought to be set up to make teachers and students talk in a low voice, add enclosures near the bathroom to reduce noise transmission, and at the same time should introduce natural sound and pleasant music with lower sound pressure level in the reading area to facilitate users' learning. 5. ACKNOWLEDGEMENTS We gratefully acknowledge the Library of South China University of Technology for providing help in the research. 6. REFERENCES 1. Ji X.R. Research on acoustic Environment of University Library. Diss. Taiyuan University of

Technology,3-4(2018). 2. Wang Z.J. Research on sound environment of university library building. Diss. Taiyuan

University of Technology, 3-5 (2015). 3. Gong C C. Study on noise environment evaluation and control of open shelf reading space of

university library in Guangzhou University Town. Diss. South China University of Technology,5 (2017).