2nd Track : Rethinking the Mosque Architecture of the Future
Role/Contribution
Author
Research paper Title
Criteria and Methods for Acoustical Evaluation of a Mosque: A Case Study of the Kobe Mosque, Japan
Personal Biography
Prof. Dr. S. M. Najmul Imam is a Professor in the Department of Architecture, Bangladesh University of Engineering and Technology (BUET), Dhaka, Bangladesh. He has received his B. Arch and M. Arch degree from BUET, while acquired his PhD degree on Building Acoustics from Kyoto University, Japan. After graduation in 1989, Dr. Imam worked as a practicing architect for five years and designed several buildings in Bangladesh and abroad. He joined as a Lecturer in the Department of Architecture, BUET in 1994 and continuing till date in different positions. His major field of teaching, research and practice is environment and energy in architecture, including acoustics, thermal comfort, lighting, sustainability and green building practice; keeping a special interest and expertise in Building Acoustics. Notably, he had been acoustical consultant of Bangladesh National Assembly Building. He has acquired skills and practical experiences on computer based parametric design methods applying acoustical simulation techniques, which is currently state-of-the-art in the field of acoustical design and assessment. He has practical experiences of designing numerous public and private projects highlighting building acoustics and other environmental issues. Prof. Imam takes building acoustics related courses both in undergraduate and postgraduate levels; supervises postgraduate research, contributes in conferences, workshops and journals. He is a Fellow in the Institute of Architects Bangladesh (IAB). He has contributed as a Member of Editorial Subcommittee and also as the Author of the Chapter 'Building Acoustics' in Bangladesh National Building Code (BNBC) 2020. Along with various academic and administrative activities, Dr. Imam has served as the Coordinator of Environment and Energy Division. He is a Member of the Executive Committee in the Green Architecture Cell (GrACe) and In-Charge of Acoustical Lab, Department of Architecture, BUET.
Paper Abstract
A satisfactory acoustical environment is one of the prime necessities of a mosque to perform major activities such as congregational prayers, theological teachings, and discussions. Acoustically, a mosque involves mainly two types of sounds: speech and melodious bare-voice recitation from the Holy Quran. Speech requires more intelligibility than liveliness, while melodious recitation requires more liveliness than intelligibility. Considering these unique inverse acoustical requirements, this study proposes criteria pertinent to the acoustical evaluation of a mosque. These include the optimum Reverberation Time (RT) balanced for both speech and melodious recitation; diffusion of Sound Pressure Level (SPL), Background Noise Level, Speech Transmission Index (STI), Rapid Speech Transmission Index (RASTI), and Clarity Index. To evaluate acoustical performance under these criteria, this paper also proposes appropriate methods, including questionnaire surveys, Percentage Syllable Articulation (PSA), Impulse Response, measurements of Background Noise Level, measurements of Sound Pressure Level (SPL), and computational parametric methods for acoustical analysis and simulation. To demonstrate these methods and fulfill evaluation criteria, a case study was conducted on the Kobe Mosque, Japan. The acoustical evaluation in the questionnaire survey rates as 1.12 on a scale from +2 to -2, which is between ‘Good’ and ‘Very good’. Impulse Response shows an average RT ranging from 1.67 s to 0.71 s for a range from 125 Hz to 8 kHz. Noise Levels (Leq) in the main prayer hall range from 39.9 dBA to 52.4 dBA under various conditions. The average STI of 0.64 and RASTI of 0.62 indicate the speech intelligibility and overall acoustical performance as ‘Good’ on a quasi-subjective scale. These physical methods of evaluation were compared with computational parametric methods and found to be similar.
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