Soundscapes in Public Libraries

Transcription

1 M. A. Schnabel (ed.), Back to the Future: The Next 50 Years, (51 st International Conference of the Architectural Science Association (ANZAScA)), 2017, Architectural Science Association (ANZAScA), pp Soundscapes in Public Libraries A Case Study Jin Woo and Priyadarsini Rajagopalan RMIT University, Melbourne, Australia {jin.woo, priyadarsini.rajagopalan}@rmit.edu.au Abstract: This study investigates the acoustic conditions of reading spaces in a public library in Melbourne. An acoustics performance survey for library users was developed to evaluate library use, sound environment and noise, and a face to face survey was conducted in the library. The library users described their sound environment as pleasant, appropriate and calm. The respondents of two reading rooms expressed a high level of satisfaction with sound environment and a neutral perception of noise, neither noisy nor quiet. Three main sources of noise, namely, footsteps, people and chair dragging were also found in the reading spaces. Interestingly, it was found that noise from lift, windows and doors opening, traffic and construction noise and noise from birds outside the building, resulted in the difference between user perceptions of noise between two reading rooms. It could be interpreted that this result was related to the library space layout, building design and building services. It is recommended that the link between architectural characteristics and space use pattern and acoustic performance be examined in public library buildings. Keywords: Soundscape; acoustics; public libraries. 1. Introduction Contemporary public libraries provide a wide range of services in addition to traditional reading spaces. Libraries have experienced increasing usage as they have transformed into multipurpose facilities, adapting to changes in technology and society. However, a substantial group of library patrons still come to the library looking for quiet reading spaces for concentrated study. Public libraries are reviewed regularly by local authorities to improve the services they provide to the citizens. As a result, more physical facilities are often provided to cope with the needs of library users and this has led to increasing noise levels, especially in quiet study and reading rooms (Franks and Asher, 2014). Proper acoustic conditions are believed to improve the effectiveness of comprehension and the development of cognitive skills. This study investigates the acoustic conditions of reading spaces in a public library in Melbourne. A pilot survey was conducted to examine overall user perception of the sound environment and noise in the library and also to identify main activities and space usage. Subsequently, two sets of user surveys were conducted in the reading rooms to investigate how the quiet spaces support users acoustically.

2 686 J. Woo and P. Rajagopalan 2. Soundscape and Noise Soundscape can be defined as human perception of acoustic environment and it refers to the acoustic environment perceived, experienced and understood by people. Acoustic environment, however, can be defined as sound at the receiver from all sound sources as modified by the environment. It can be actual or simulated, outdoor or indoor, as experienced or in memory (ISO, 2014). The human ear senses sound based on the frequency and strength of vibrations, being affected by the listener s health state and age. Thus, a complex sound such as noise in daily life can be difficult to measure as it is due to high frequency overtones. Acoustic comfort has been studied in the architectural science discipline using objective environmental measurements (Rajagopalan et al., 2016) and in combination with subjective measures (Chen and Kang, 2004; Dokmeci and Kang, 2012; Aremu et al., 2015). Noise can be defined as unwanted sound with random vibrations and no regular pattern. It is the major source of distraction in a concentrated work environment such as offices, classrooms and libraries. It was found that various distractions such as noise from telephones, conversations, building systems and office equipment were related to openness of space plan and such distractions from noise is one of the most frequent complaints among office workers (Brookes and Kaplan, 1972; Hedge, 1982; Sundstrom et al., 1994; Lee and Brand, 2005). Noise from conversations can adversely influence high level cognitive work such as logical thinking, continuous access to working memory and concentration, and interrupt these internal processes (Heerwagen, 2000). In public libraries, noise problems caused by deficient acoustic design can be divided into: noise coming from outside due to poorly insulated facades, lack of consideration in separating quiet and noisy areas, excessively reverberant spaces with limited absorption, and poor speech intelligibility. The level of acceptable noise depends on subjective psychological factors such as the state of mind and expectations of the listener as well as objective physical ones (Szokolay, 2014). Similarly, the responses to noise not only rely on its physical properties such as degree of loudness, but also on the individual s sense of control (Sundstrom, 1986). 3. Research Design The State Library of Victoria which is a landmark and cultural icon of Melbourne was selected as a case study. The library is located in the centre of the city and accommodates 1.8 million visitors annually. It also employs 259 staff as one of Australia s oldest cultural institutions. Architecturally, it is a nineteenth century Victorian Period Academic Classical style building listed on the Victorian Heritage database (Heritage Council Victoria, 2008; State Library Victoria, 2017). Figure 1 shows the floor plan of the library showing the two reading rooms namely Redmond Barry reading room and La Trobe reading room which is also known as the Dome. Acoustic evaluation was mainly conducted through user survey. The survey results were later analysed in conjunction with the sound levels measured in the respective reading rooms.

3 Soundscapes in Public Libraries User Survey Figure 20: Schematic floor plan An acoustics survey for library users was developed to evaluate the pattern of usage, sound environment and noise. The library use includes visit frequency, time spent, type of activity performed and space used. In order to measure the user perception of sound environment, the Swedish Soundscape Quality Protocol (SSQP) was adapted in the survey. Axelsson et al. (2010) developed a principal components model of soundscape perception, identifying the eight adjectives (i.e. pleasant, exciting, eventful, chaotic, annoying, monotonous, uneventful and calm) considered as equally distant and strong semantic concepts in relation to soundscape in the model. Employing the eight adjectives, perceptual ratings of sound environment were measured on a 5 point Likert type scales (5= strongly agree to 1= strongly disagree). The overall acoustic satisfaction was also questioned using a 5 point Likert type scales (5 =very satisfied to 1=very dissatisfied). In order to identify noise sources in the library, a total of thirteen noise sources were identified and measured on a 5 point Likert type scales (5=very noisy to 1=very quiet). The noise sources include those resulted from user behaviour (e.g. conversation, page turning, footsteps, chair dragging), equipment (e.g. photocopiers, printers), building services (e.g. HVAC, lighting, lift), building (e.g. windows and doors opening), outside building (e.g. traffic, construction) and sound from nature (e.g. trees and birds). Participants were asked about the overall perception of noise using a 5 point Likert type scales (5 =very noisy to 1=very quiet). Two additional questions about noise control methods and preferred actions to be taken to control noise in the library were also asked. A two page structured questionnaire, entitled acoustics performance of public libraries for users, was developed and a face to face survey was adopted to achieve a higher response rate. The survey was granted ethics approval Acoustic Measurement Sound levels at various locations inside the selected rooms were measured using a Bruel & Kjaer handheld analyser Type 2270 (Figure 2). The sound is captured by the Brüel & Kjær Prepolarized Free field ½ microphone with a wide frequency range. The measurements were conducted in compliance with the Australian Standards for noise measurement (AS/NZS 2107, 2000) and the methods prescribed by Environmental Protection Agency guidelines (EPA, 1991). The microphone is placed away from shielding,

4 688 J. Woo and P. Rajagopalan reflecting, or absorbing objects during the measurement. Sound levels were recorded continuously for a period of 15 minutes at each location. The average noise levels (LAeq) measured in dba were used for analysis. 4. Results and Discussion 4.1. Pilot Study Figure 2: Sound level meter used for the measurement A pilot survey was conducted in the foyer (refer to Figure 1) of the state library to understand the duration of stay, main activity and main location where users spend most of the time in the library. A total of 29 responses were collected through a face to face survey on a Friday afternoon. Less than half of the respondents used the two reading rooms (Redmond Barry reading room and La Trobe reading room as shown in Figure 1) which can be classified as quiet spaces, and the rest of the respondents stayed at the information centre on the ground or at the Dome gallery/dome viewing balcony during their visits (Table 1). Table 2: Main location where users spent most of the time in the library. N Level 2/Ground Information Centre 7 Redmond Barry Reading Room 8 La Trobe Reading Room 5 Dome gallery, balcony, etc 8 Total 28* *one missing response

5 Soundscapes in Public Libraries 689 The user perception of sound environment was measured by the eight adjectives identified in the Swedish Soundscape Quality Protocol (Figure 3). The respondents described their sound environment as pleasant (4.15 out of 5), appropriate (4.07 out of 5) and calm (3.96 out of 5), reporting an overall satisfaction of The user perception of noise was evaluated using the thirteen noise sources (Figure 4). The library users showed an overall perception of noise 2.61 out of 5 which can be interpreted as neither quiet nor noisy, close to a neutral point. They also pointed out footsteps (2.69), people (2.34), and chair dragging (2.24) as main noise sources in the library. Figure 3: User perception of sound environment Figure 4: User perception of noise Two additional questions about noise control methods and preferred actions to be taken were asked (Table 2 and 3). Half of the respondents indicated they used a noise blocker when they were distracted. Approximately one third would either move to a quiet area in the library or leave the library when they got distracted by noise. However, only one respondent would make a complaint to the library. Furthermore, a majority of the library users prefer quiet zone signage to other actions such as background sound and building sealed. Table 3: Noise control methods. Table 4: Preferred actions to be taken. N Move to a quiet area in the library 7 Leave the library 4 Use a noise blocker 13 Make a complaint to the library 1 Other 1 Total 26* *two missing responses N Quiet zone signage 18 Background sound 4 Building/doors/windows well 6 sealed Other 3 Total 31* *multiple answers

6 690 J. Woo and P. Rajagopalan 4.2. Acoustics Performance of Reading Spaces Library user surveys were conducted to investigate the sound environment and noise in two reading rooms: Redmond Barry reading room and La Trobe reading room (Figure 5). The Redmond Barry reading room has a floor area of 800 m 2 and a 15 m high ceiling and the La Trobe reading room has a floor area of 1000 m 2 with a 35 high domed ceiling. Figure 5: Redmond Barry and La Trobe reading rooms The sound level measured (according to the procedure explained in section 3.2) in the La Trobe reading room ranged between 49.6 db and 51.2 db. The sound level in the Redmond Barry reading room ranged between 45 to 47 db. The balcony space of the Redmond Barry reading room is very popular among students as they provided quiet reading spaces. The sound levels measured in these spaces were between 44.5 to 45 db. The user perception of the sound environment in the two reading rooms is shown in Figure 6. A total of 74 responses from two reading rooms (N=37 from each reading room) were analysed and compared by mean scores. The respondents of both reading rooms described their sound environment as appropriate, calm and pleasant, reporting the overall satisfaction of 4.05 with sound environment. This result is consistent with the result of the pilot study, which could be interpreted that the user perception of the library is likely to be in common regardless of space use or main activity, i.e. whether it is a quiet space or a space for other purposes. Figure 6 demonstrates the mean scores of the sound environment perceived by the library users in the Redmond Barry reading room (in blue) and the La Trobe reading room (in red). To determine if differences between the acoustics perception of two reading rooms are statistically significant, an independent sample t test was conducted. The purpose of the independent sample t test is to test for a statistically significant difference between two independent sample means, which are the user perception of sound environment in Redmond Barry reading room versus La Trobe reading room. In this circumstance the concern is not with the absolute values of means, but with the significance of the difference between them. It was found that the only adjective, uneventful (p<0.05, two tailed) showed a statistically significant difference between two reading rooms. The respondents of the Redmond Barry reading room described more uneventful (3.17) than those of the La Trobe reading room (2.58).

7 Soundscapes in Public Libraries 691 Figure 6: User perception of sound environment in reading spaces To examine the sources of noise in the quiet reading rooms, the perception of noise was evaluated by the library users. Not surprisingly, the main sources of noise were found to be the same as those identified from the pilot study: footsteps, people and chair dragging (Figure 7). The library users expressed a neutral perception of noise, 2.21 in the Redmond Barry reading room and 2.51 in the La Trobe reading room respectively. Figure 7: User perception of noise in reading spaces To determine if differences in noise between two reading rooms are statistically significant, an independent sample t test was conducted (Table 4). Five noise sources out of thirteen showed statistically

8 692 J. Woo and P. Rajagopalan significant differences between the Redmond Barry reading room and the La Trobe reading room: Footsteps, Lift, Building, Outside building and Outside. These five sources were found to be relatively quieter except footsteps, however, differences are statistically significant. The respondents in the La Trobe reading room felt noisier with noise sourced from Lift, Building, Outside building and Outside compared those in the Redmond Barry reading room. Interestingly, the library users in the Redmond Barry reading room perceived more noise sourced from footsteps. Table 5: Comparison of noise sources between Redmond Barry and La Trobe Reading Rooms. Redmond Barry La Trobe t df p People (conversation) Page turning Footsteps * Chair dragging Mobile device Books dropping Equipment Book trolleys HVAC/lighting Lift * Building * Outside building * Outside ** * p<.05, ** p<.01 (2 tailed) It can be seen that sound levels measured with the presence of occupants is higher in The La Trobe reading rooms compared to Redmond Barry reading room. In a previous study, Rajagopalan et al. (2016) measured the background noise levels without occupants in the state library. The authors found that the background noise levels measured in the La Trobe reading rooms were higher (40 db) than those measured in the Redmond Barry reading room (38.5 db). The reverberation time (RT) measured in the La Trobe reading room was up to 5.6 sec and the RT measured in Redmond Barry reading room was up to 2.6 sec. High volume of the La Trobe reading room contributes to the high RT. Furthermore, speech intelligibility was found to be worse in La Trobe reading room compared to Redmond Barry reading room. However, poor speech intelligibility corresponds to good speech privacy that can support group study environment. Building on previous research, it was found that noise sources such as lift, building windows and doors opening, traffic and construction noise from outside building, outside nature sound like trees and birds caused statistically significant differences between the noise perceptions in the two reading rooms. These noises are produced from building design and operation, the location and transmitted through the building facade. It seems that the La Trobe reading room has a lot more architectural significance which also attracts a large volume of visitors, compared to the Redmond Barry reading room. 5. Conclusion Although public libraries have been transformed into multipurpose facilities and adapted to changes in technology and society, the role of traditional reading spaces is crucial to support a substantial group of library patrons who need quiet reading spaces for concentrated work in the libraries. It is evident that

9 Soundscapes in Public Libraries 693 proper acoustic conditions could improve the effectiveness of comprehension and the development of cognitive skills. This study investigated the acoustic conditions of reading spaces in a public library in Melbourne. An acoustics performance survey for library users was developed to evaluate library use, sound environment and noise, and a face to face survey was conducted in the library. The library users described their sound environment as pleasant, appropriate and calm regardless of their space use and main activity in the library. Acoustic performance in the two reading rooms was found to be acceptable based on both measured sound levels and user survey. The library users reported a high level of satisfaction with sound environment and a neutral to quiet perception of noise. Although three main sources of noise ( footsteps, people and chair dragging ) were also found in the reading spaces, the library users perception of the noise sources is closer to neutral and quiet except the footsteps in the Redmond Barry reading room. This can be explained by the old hardwood flooring in the room. Interestingly, statistically significant differences were found in building design related noises such as lift, building windows and doors opening, traffic and construction noise from outside building, and sound from birds outside. Although these noise sources do not seem to cause critical acoustic issues in the library, they are all related to the library space layout, building design and building services. Therefore, it is recommended that the link between architectural characteristics and space use pattern and acoustic performance in public library buildings be examined to achieve high levels of acoustic performance. The next stage of the study involves calculation of psychoacoustic descriptors for each room using the audio recordings. Acknowledgements The authors would like to thank the State Library of Victoria and Mr Anthony English, Property Manager, State Library of Victoria for assisting with access and setting up of the user surveys. References Aremu, A. S.,Omoniyi,J.O. and Saka, T. (2015) Indoor noise in academic libraries: A case study of University of Ilorin Main Library, Nigeria, African Journal of Library, Archives & Information Science, 25(1), AS/NZS Acoustics Recommended Design Sound Levels and Reverberation Times for building Interiors. Sydney: Standards Australia. AS/NZS Acoustics Measurement of the Reverberation Time in the Rooms. Sydney: Standards Australia Axelsson, O, Nilsson, M.E. and Berglund, B. (2010) A principal components model of soundscape perception, Journal of the Acoustical Society of America, 128(5), Brookes, M. J. and Kaplan, A. (1972) The office environment: Space planning and affective behavior, Human Factors, 14, Chen, B. and Kang, J. (2004) Acoustic comfort in shopping mall atrium spaces A case study in Sheffield Meadowhall, Architectural Science Review, 47(2), Dokmeci, P., and Kang, J. A. (2012) Comparative case study of indoor soundscape approach on objective analyses and subjective evaluations of libraries, Acoustics 2012 Nantes Conference, Nantes, France, April EPA Victoria A Guide to the Measurement and Analysis of Noise. Available from: < /media/publications/280.pdf> (accessed April 4, 2015). Franks, J. E. and Asher, D. C. (2014) Noise management in twenty first century libraries: case studies of four U.S. academic institutions, New Review of Academic Librarianship, 20, Hedge, A. (1982) The open plan office: A systematic investigation of employee reactions to their work environment, Environment and Behavior, 14, Heerwagen, J. (2000) Green buildings, organizational success and occupant productivity, Building Research and Information, 28,

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