Acoustical Requirements in Architectural Design Studios

Transcription

1 Acoustical Requirements in Architectural Design Studios Asli Ozcevik Anadolu University, Faculty of Engineering and Architecture, Department of Architecture, 26470, Eskisehir, Türkiye, Zerhan Yüksel Yildiz Technical University, Faculty of Architecture, 34349, Istanbul, Türkiye, Architectural design studios are particular spaces of architectural education which implicates an education psychology including the basic principle of knowing-in-action. They are original classrooms where professional and cultural information are transferred to architectural students, design methodologies and doctrines are discussed and design alternatives are practiced. There is a continuous flow of knowledge that covers verbal and visual communication among the occupants through the studio based educational system. In studios, several different functions, unique to architectural education take place simultaneously. Simultaneous happening of different functions create different design requirements, hence oblige to the flexible usage of space and a special acoustical environment having specific acoustical requirements. This relation constitutes the proper acoustical environment that is defined by noise control and room acoustic parameters. In this study, at first, acoustical requirements specific to architectural design studios will be determined based on the general concepts of acoustical comfort for educational and open-plan spaces. According to these data on the conditions of proper acoustical environment, one of the architectural design studios of Department of Architecture at Anadolu University in Eskisehir/ TURKIYE will be analyzed as a case study. The noise control and room acoustic parameters of the studio will be measured and evaluated. 1 Introduction Architecture is an interdisciplinary field that comprises several major components: humanities, social and physical sciences, technology and creative arts [1]. Architectural education covers the original combination of traditional education and design centered, studio based methodologies. It uses unique approaches that combine method aided creativity of several fields like art, mathematics, technology, philosophy, theory and history [2]. According to UNESCO / UIA Charter for Architectural Education (1996), the basic goal of this education is to develop the architect as a generalist able to resolve potential contradictions between different requirements, giving form to the society s and the individual s environmental needs [3]. Architectural design studios are particular spaces of architectural education which implicates an education psychology including the basic principle of knowingin-action, the tradition of studio-based education system which often seems innovative when it is introduced to other professional education system [4]. In this education system there is a continuous flow of knowledge that covers verbal and visual communication among the occupants during the education process. The usage of the space is spread out to the whole educational process -not only in the main study hours but also in the free times of the students. This means; students spend long hours in design studios which is the basic space and communication channel of architectural education. For this reason, it is clear that there is a life process creating continuous development of learning at this environment. This is the most important property that exhibits the difference between design studios and other classrooms. Proper physical environment which depends on visual, acoustical and thermal comfort conditions should be formed to support the education system by realizing a high quality verbal and visual communication. In studios, several different functions unique to architectural education take place simultaneously. Because of the importance of verbal communication and the simultaneous happening of different functions, studios should have a flexible design that permits a proper spatial usage and a special acoustical environment having specific acoustical requirements. Providing the proper acoustical environment, that is defined by noise control (acceptable external noise level, acceptable background noise level, Sound Transmission Loss values of building components) and room acoustic parameters (RT, D50, SPL, S/N, STI- RASTI and Acoustical Problems), should be one of the primary design objectives in architectural design studios. A study is realized to determine the acoustical requirements specific to architectural design studios based on the general concepts of acoustical comfort for educational and open-plan spaces. According to these data on the conditions of proper acoustical environment, one of the architectural design studios of the Department of Architecture at Anadolu University in Eskisehir/ Türkiye is examined and exemplified as a 2053

2 case study. The noise control and room acoustic parameters of the studio are measured and evaluated. 2 Acoustical requirements of the architectural design studios Architectural design studios are original classrooms where professional and cultural information are transferred to architectural students, design methodologies and doctrines are discussed and design alternatives are practiced. The main goal at design project is to develop proposals about design problems and to improve design skills. Design project work must be a synthesis of acquired knowledge and concomitant skills similar to the education in traditional classrooms. In studios, there is an old tradition of education for the exercise of artistry. The studio tradition builds examples of practice and critical reflection on practice, into the core experience of learning architectural design. Design education is organized around projects of design, individual or collective, which are more or less closely patterned on projects drawn from actual practice. The studio contains its own traditional events; Master demonstrations, Design reviews, Desk crits (critics), Juries - all of which have grown up around the central theme of practice in designing [4]. Johnson (2000) has systematically classified these functions as formal and informal functions. Formal functions are general information, individual study, desk critics, group study, group critics and jury critics; informal functions are to observe a successful methodology or product strategy in the studio, to follow design reviews, juries and desk critics of the other students and to participate the discussions or design reviews considering the already achieved design problems [5]. Each function unique to design studios has different spatial and acoustical statements and because of this different acoustical requirements. Design studios should be designed with the concept of flexibility providing spatial and acoustical requirements of the space functions which are changeable and unique to this special room type. Interconnecting and simultaneous happening of the functions realized at the studios led us to consider these as a kind of multi-purpose and open-plan spaces (openplan office and open-plan classroom). The basic requirements of acoustic comfort for traditional classroom can be listed as; to ensure background noise level at optimum limits, to provide speech intelligibility and to prevent acoustical problems. The fundamental acoustical relation between traditional classroom, open-plan spaces and architectural design studio may be used to constitute the proper acoustical environment of studios. By the goal to utilize the similarities and differences between open-plan office, traditional classroom, open-plan classroom and architectural design studio, a comparative study has been realized taking into account space parameters, acoustical and architectural requirements. Table 1 summarizes this study and gives the acoustical requirements as well as practical solutions to create optimum acoustical environment in design studios. Because the architectural designs/layouts of these spaces are also effective factors that define the relation, they are taken into account in Table 1. Traditional classrooms are small spaces designed for approximately students; open-plan spaces are usually designed larger than traditional classrooms for serving to the occupant capacity of the space. According to observations, design studios tend to be approximately between 120 and 600 m 3 in volume for students. Acoustic barriers, which are used to provide privacy and acoustical shadow in open-plan spaces designs, are included in Table 1, considering their effective role to improve the acoustical comfort. The flexible application of the acoustic barriers can be used as a tool to obtain the acoustical requirements (both for privacy and increasing the total sound absorption) in architectural design studios. 3 A case study; an architectural design studio of the Department of Architecture at Anadolu University Department of Architecture at Anadolu University in Eskisehir constructed in 1999, is designed as an educational building at a distance about 10 km from the city centrum. The dominant noise source is the aircraft noise from training airport of the School of Civil Aviation in the campus and the military airport at a distance about 8 km from the campus. Because acoustic comfort condition has been neglected during the design process of the building, there are some serious acoustical problems. In order to exemplify the acoustical situation, Studio 2 is chosen to work on where parameters related to noise control and room acoustic have been measured. Considering the variable usage related to the different functions and their spatial requirements, the actual spatial arrangement designed by the students is accepted during this process. Figure 1 shows the plan scheme of Studio 2 in which different functions such as general information, individual study, desk critics, group study and group critics exist simultaneously and/or singly and the adjacent spaces with source (S) and receiver (R) positions. Table 2 gives information about the physical and architectural properties of the studio. 2054

3 Table 1. Comparison of space parameters, acoustical and architectural requirements of open-plan offices, traditional classrooms, open-plan classrooms and a proposal for acoustical and architectural requirements for architectural design studios Space Parameter Open-plan offices Traditional classrooms Open-plan classrooms Concept Productivity Education Education Architectural design studios Practice based education Basic principle Flexibility Traditional education arrangement Flexibility Flexibility Privacy Design problems External noise level Background noise level Acoustical, visual, informative Sound transmission/noise control Sound masking Noise control Speech intelligibility Acoustical problems - Acoustical Acoustical Acoustical requirements Background noise Speech intelligibility Background noise Speech intelligibility Acoustical problems db (LeqA) db (LeqA) db (LeqA) Sound masking sys. NC40 48 dba(+/- 2 db) NC dba NC35 45 dba NC dba STC IIC RT- upon the as short as volume of the space possible sn sn sn D50 Low D50 ratio % 50 % 65 % 65 S/N closely 0 or if possible 0 db 15 db 15 db 15 db STI-RASTI Low STI-RASTI value >0.60 >0.60 >0.60 Architectural requirements to obtain good acoustics Floor Absorbent Absorbent Absorbent Absorbent Walls Absorbent Absorbent-Reflectent Absorbent Absorbent Furniture Absorbent Absorbent-Reflectent Absorbent Absorbent Acoustic barrier (height) Relation between occupants 1.7 m Avoid line of sight and pathway of - Traditional education arrangement 1.7 m and/or storey height-0.5 m Avoid pathway of 1.7 m and/or storey height-0.5 m Avoid pathway of Ceiling Absorbent Absorbent-Reflectent Absorbent Absorbent-Reflectent 2055

4 Figure 1. The plan of the Studio 2 and source(s), receiver(r) positions Table 2. Physical-architectural properties of the Studio 2 Dimensions of the studio l: 19 m, w: 9.2 m, h: 3.2m. S= 530 m 2 V= 560 m 3 N= 56 Unit/Surface Number /S(m 2 ) Material Students Tabourets 56 All surfaces are wood and plywood Drawing/model construction desks 60 Two sides laminated 18 mm fiberboard Wall 110,7 Cement plastered brick Ceiling 175 Lime plastered concrete and brick Floor 115 Mosaic tiles Window 33,7 Double glazed Window 11,3 Single pane Door (2) 8,3 2 surfaces pressed with 8 mm. plywood Chalkboard 3.2 Hard wood panel Boards 13,3 Hard wood panel In order to try to assess the acoustic field in Studio 2, at first some measurements on external noise are made. Because NEF contours of the nearby airports have not been displayed systematically the external noise level is measured due to the two conditions, with and without flights. The external noise is measured 46 db (LeqA) without flights and 77 db (short time LeqA) during flights. The external noise occasionally increases up to db (short time LeqA) by the landing and taking off directions and situations of aircrafts. The training aircrafts flight density has an average of 325 hours per month at the term of a year between April and October, also according to the weather conditions. The military aircraft flights have an average of 330 hours per month not depending on the weather conditions throughout the whole year. Therefore, it is clear that although when the flights are not considered, measured external noise level is within the acceptable limits, there is a serious noise problem due to aircraft noise. Ensuring the background noise level at optimum limits is essential to provide speech intelligibility in a space. Background noise level of the Studio 2 without flight is measured about 36 db (LeqA) which is a value within the acceptable level interval. Consequently, this case provides the required S/N ratio (S/N 15 db), considering the normal speech level 60 db for intelligibility in the studio. We were not able to repeat these measurements during flights, but still it can be said that indoor noise levels risks to be higher than acceptable levels depending on the flight conditions. The sound insulation is measured according to ISO 140/5 for facade elements/facades and ISO 140/4 for buildings and building elements, at three locations. These measurements are done respectively between Studio 2 and outside for external walls, between Studio 2056

5 2 and adjacent spaces (Studio 1 and the corridor) for internal walls. Depending on measured SPL values, Sound Reduction Index is calculated on each location (Figure 2). It is determined that the sound insulations of the external and internal walls are far away to provide the required sound insulation given at Table 1. Sound Reduction Index (db) ,9 17,9 30,5 25,4 19,6 32,7 26,5 20,7 34,9 24,8 22,5 33,1 22,3 20, Frequency (Hz) Studio 2 and outside Studio 2 and Studio 1 Studio 2 and corridor 26,7 22,3 19,7 evaluating this parameter, results at mid-frequencies are considered because relatively proper approach for speech. This parameter has an appropriate ratio of % 27 at mid-frequencies in this studio as seen in Figure 4. D50 (%) ,6 26, Mid-frequency (Hz) required-minimum-d measured D50 Figure 4. Average D50 of Studio 2 at mid-frequencies To assess the acoustical quality of educational spaces, STI-RASTI should also be evaluated. Considering this, the measured values for 2/3 occupied and unoccupied situation of the Studio 2 and the regarded meanings of the STI-RASTI values are shown in Figure 5. Figure 2. Average values of Sound Reduction Index for the external and internal walls Room acoustic parameters including the reverberation time (RT) are measured according to ISO 3382 for the occupied and unoccupied room. Measured and optimum RT s for unoccupied studio at octave frequencies are given in Figure 3. It is seen that the actual RT s are significantly higher than the optimum RT values, especially for low frequencies. EDT is also evaluated for this studio in the same figure. The results displays the acoustic environment of the space is inadequate similar to the RT results. Reverberation Time-RT&EDT (sn) 4,00 3,50 3,00 2,50 2,00 1,50 1,00 0,50 0,00 3,70 3,40 3,10 3,00 2,50 2,30 2,00 1, optimum-maximum-rt average measured RT Frequency (Hz) optimum-minimum-rt average measured EDT 1,20 0,90 0,62 Figure 3. Optimum average measured RT s and average measured EDT s for unoccupied situation of Studio 2 An important acoustic parameter to measure the speech intelligibility of a space is the Definition (D50). While Figure 5. Average STI-RASTI for 2/3 occupied and unoccupied situation of Studio 2 and meanings of the STI-RASTI values Acoustical and architectural recent situations are given in Table 3 compared to the values in Table 1. As seen from the Table 3, acceptable external and background noise levels are satisfied in Studio 2 when the flights are disregarded. The condition that provides the background noise level at acceptable limits is also appropriate to the required S/N ratio. However, because the sound insulation of the building components including external and internal walls are not sufficient, the required background level will not be satisfied depending on the presence and conditions of flights. Because almost all surfaces of the studio are reflective and the number of occupants in the room is less than the number given in the literature for such a volume size, the actual RT s and EDT s of the studio is very high especially at low frequencies. Furthermore, D50 parameter is not obtained at the required ratio which is above %65. Even though the intelligibility in design studios should be above STI 0.6, this value is lower than the limit value in Studio 2. On the other hand, first studies showed that there are no specific acoustical problems such as echo and focusing in the studio. 2057

6 Table 3. General estimation of the measurements in Studio 2 based on the acoustical requirements of architectural design studios External noise level Background noise level Architectural design studios Studio 2 (without flights) db (LeqA) 46 db (LeqA) NC dba 36 db (LeqA) STC 50 < 50 IIC RT sn sn D50 % 65 % 27 S/N 15 db 15 db STI-RASTI >0.60 < 0.60 Floor Absorbent Reflectent Walls Absorbent Reflectent Furniture Absorbent Reflectent Acoustic barrier (height) Relation between occupants 1.7 m and/or storey height-0.5 m Avoid pathway of Unused Neglected Ceiling Absorbent-Reflectent Reflectent 4 Summary In this study, acoustical requirements specific to architectural design studios are determined based on the general concepts of acoustical comfort for educational and open-plan spaces. Basic similarities and differences from the acoustical requirements of traditional classrooms and open-plan spaces are defined to occur from the multi-purpose usage of the room and variable spatial design. The analyze as a case study of an architectural design studio of the Department of Architecture at Anadolu University in Eskisehir/Türkiye, showed that the acoustical properties are inadequate. This case has been demonstrated with the measurements of noise control and room acoustic parameters. The resultant evaluations of the measurements are similar to the subjective evaluations of the occupants. As seen at this research, the acoustical requirements in architectural design studios differ from traditional classrooms. Detailed studies illustrating the proper acoustical environment in studios can be developed according to the suggestions given at Table 1. References [1] N. Ayıran, Mimari tasarım stüdyoları üzerine bazı notlar, Yapı 160, pp , (1995) [2] H. Gökmen, D. Süer, Mimari tasarım stüdyosunun elemanları, Ege Mimarlik, Chamber of Architects Izmir Branch, pp. 6-7, (2003) [3] UNESCO / UIA Charter for Architectural Education, Barcelona, Spain, [4] D. Schön, The design studio, published RIBA Publications Limited, printed Frank Peters Ltd., London, England, 1985 [5] B.R. Johnson, Sustaining Studio Culture: how well do internet tools meet the needs of virtual design studios? On education in Computer Aided Architectural Design in Europe, pp , (2000) [6] Z. Karabiber, M. Vallet, Some European policies regarding acoustical comfort in educational buildings. Noise Control Engineering Journal 50(2), pp , (2002) [7] E. İşler, Kentsel ölçekte gürültünün denetlenmesinde engel etkinliğinin incelenmesi, Master of Science Thesis, Yildiz Technical University, Istanbul, 2005 [8] Regulation Draft of Environmental Noise Evaluation and Management, 2004 [9] Building Bulletin 93, Acoustic Design of Schools; A Design Guide, Architects and Building Branch, London, 2003 [10] Acoustical Society of America, American National Standard, Acoustical Performance Criteria, Design Requirements and Guidelines for Schools, New York, 2002 [11] ASID Sound Solutions Increasing Office productivity through integrated acoustic planning and noise reduction strategies, USA, 2004 [12] V. Hongisto, J. Keranen, P. Larm, Prediction of speech transmission index in open-plan offices. Joint Baltic-Nordic Acoustics Meeting, Aland, 2004 [13] L.K. Irvine, R.L. Richards, Acoustics and noise control handbook for architects and builders, Kruiger Publishing Company, Florida, 1998 [14] T. Malet, Acoustique Des Salles, Publications Georges Ventillard, France, 2001 [15] [16] D. Templeton, Acoustics in the Built Environment, Architectural Press, Oxford,