Title Optimization of Reverberation Time in Mosques for Bangla
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Optimization of Reverberation Time in Mosques for Bangla Title Speaking Community( Dissertation_全文 ) Author(s) Sheikh, Muhammad Najmul Imam Citation 京都大学 Issue Date 2017-03-23 URL https://doi.org/10.14989/doctor.r13091 Right Type Thesis or Dissertation Textversion ETD Kyoto University Optimization of Reverberation Time in Mosques for Bangla Speaking Community Sheikh Muhammad Najmul Imam SUMMARY Summary A mosque resembles with a large hall room having almost no furniture as the floor is used for all activities. Acoustically, it involves mainly two types of sounds - speech and melodious recitation. The recitation from the Holy Quran is performed melodiously in bare voice without any musical instrument. Speech requires more intelligibility than liveliness, while melodious recitation requires more liveliness than intelligibility. On the other hand, theologically, it is compulsory to listen attentively to the recitation of the Imam during prayers, while getting meaning of each word is optional. When the part of the Holy Quran is recited in speech, it is usually translated into Bangla in the mosques of Bangla speaking community. Due to these reasons, intelligibility for recitation is less demanded. This study sets out a balanced optimum Reverberation Time (RT), which may satisfy requirements of intelligibility and liveliness for both speech and recitation, without depriving either of those severely. Speech intelligibility is affected by speech level, Reverberation Time, noise level and space geometry. Required speech level in a mosque is attainable either by bare voice in small capacity mosques or by sound reinforcement system in large capacity mosques. Thus, intelligibility of a mosque does not usually suffer from low speech level. As a solemn and sacred worship space, a calm and quiet environment is ritually maintained in a mosque. Thus, the background noise, as one of the factors affecting intelligibility, is less significant. Most of the mosques are designed in rectangular shape, which is assumed to contribute best for speech intelligibility. As a mosque is basically furniture free large hall room with mostly reflecting i SUMMARY surfaces, it causes remarkably high Reverberation Time, which is the most significant factor more often affects intelligibility. For deriving optimum RT in a mosque, a subjective evaluation on preferences is performed using paired comparison test, to assess intelligibility and liveliness, for both speech and recitation in different RT. As Bangla phonetic characteristics differ significantly from those of English, the effect of RT also found to be remarkably different through Percentage Syllable Articulation (PSA) test. It is also found that the nature of errors in PSA test is also unique for Bangla compared to those of English. Before completion of this study, effect of RT on Bangla speech was erroneously assumed as equal to that of English. But findings of this study shows, the recommended RT for Bangla speech is more stringent than English. In the Bangladesh National Building Code, finding of this study have been recently replaced with those of English. For performing PSA and Paired Composition Tests, some fundamental test materials on Bangla are also derived. The list of International Phonetic Alphabets (IPA) representing Bangla alphabets is revised and updated. Relative Frequency of occurrence (RFO) for Bangla phonemes, meaningless syllable sets for PSA test, speech and recitation test clips for paired comparison test, average Articulation Rate (AR) for Bangla speech and Arabic recitation in mosques is also obtained to guide articulation speed during tests on speech and recitation. This study primarily sets optimum RT in mosques for Bangla speaking people. Moreover, its findings, methodology and fundamental test materials may be helpful to derive effects of other factors on speech in Bangla or any other language. ii Contents 1 Introduction 1 2 Effects of Reverberation Time on Bangla 9 2.1 Introduction 9 2.2 Materials and Methods 15 2.3 Results and Discussions 22 2.4 Conclusions 27 3 Nature of Errors Due to Effects of Reverberation Time 29 3.1 Introduction 29 3.2 Materials and Methods 31 3.3 Results and Discussions 32 3.4 Conclusions 40 4 Optimum Reverberation Time in Mosques for Bangla Speaking Community 41 4.1 Introduction 41 4.2 Materials and Methods 46 4.3 Results and Discussions 49 4.4 Conclusions 59 5 Conclusions 60 References 64 Research Performance 71 Acknowledgements 73 iii CHAPTER 1. INTRODUCTION Chapter 1 Introduction The word 'mosque', the English version of the Arabic word 'masjid', refers to a place of prostration (Rahman 2012). Phenomenally, any place, which is used and also maintained for prayer (denotes to the original Arabic word salat) (Rahman 2012), can be defined as a mosque; a shelter is not a liturgical necessity. However, for climatic protection, privacy, maintenance, identity and other necessities - a built form with prayer spaces and service facilities is popularly defined as a mosque. It plays significant role in spiritual and practical life of a Muslim at personal and communal level. Inception of a mosque was characterized with simplicity and austerity; gradually it evolved in to splendour and monumentality (Hillenbrand 1994). A mosque plays a vital role as a centre for Islamic spirit, rituals and divine services in Muslim community. A mosque is a well-known building type in the Muslim settlements and even in the whole world. Performing mandatory prayers (refers to the original Arabic word fard salat) in a congregational group (jama'at) is regarded as a regular practice of the Prophet (peace be upon him) (sunnah mu'akkadah) or even as an obligatory (wajib) performance in Islam (Thanuvi, 1990). So, it is a common practice that a Muslim community builds a 1 CHAPTER 1. INTRODUCTION mosque to meet the fundamental religious requirement of communal prayers and other religious and social services. Thus, a mosque becomes the emblem and the impetus of the Islamic way of life and forms as an inseparable part of Muslim settlements. Apart from the principal religious and social purposes, a mosque also symbolises the identity for a community. Major activity performed in a mosque is prayers (salat); daily five times prayers, Friday prayer (jumu'a) and special prayers in the month of Ramadan. Prayer for the deceased and Eids (two major Muslim festivals) are also performed in a mosque due to inclement weather or scarcity of outdoor spaces, which are otherwise recommended for performing in open space. Other than prayers, various activities are also performed in a mosque, like religious education, practice for jikr (formal way of remembering the Almighty), dawah (preaching), religious lectures, marriage, resolving social disputes and so on (Imam 2000). A mosque is characterised by its simplicity, clarity and transparency of space (Brown 1956). The early mosques were very simple; a shelter with a single chamber, mostly rectangular in plan. With the expansion of Muslim community around the world, mosques have followed certain degree of transformation in terms of volume, aesthetics, structure, climatic features, material, construction system and others. However, the fundamental design principles remain almost the same. The elements of a mosque of mediaeval period and many of those in contemporary period usually comprises of prayer hall (liwan), cloister (riwak), courtyard (sahn), ablution (wadu), toilets and other services, prayer niche 2 CHAPTER 1. INTRODUCTION (mihrab) and pulpit (mimbar). The minaret was not present during the inception of the mosque, rather it was added afterwards (Creswell 1989, Hillenbrand 1994). Other uncommon components are ruler's gallery (maqsura), women's (zenana) gallery etc. In early Islamic mosques of Bangladesh and neighbouring areas, several niches (mihrab) were found as a common feature (Ahmed 1997), which is seldom found in contemporary ones. Bangla (ISO 639-3 ben), also written as Bengali, is a member of the Indic group of the Indo-Iranian or Aryan branch of the Indo-European family of languages (Chatterji 1979). As the state language of Bangladesh, Bangla is spoken by about 98.2% of total population in the country. It is also native to some regions of Southeast Asia including the Indian states of West Bengal, Assam, Bihar, Orissa, Tripura, etc. Bangla is also spoken by expatriates in many countries of the world. With nearly 230 million of total Bangla speakers in the world, Bangla is one of the most widely spoken languages, ranking sixth (Encarta 2006) or seventh (Banglapedia 2015, Gordon 2005) in the world. The majority of the Bangla speaking population in the world, about 74% of the total, lives in Bangladesh alone. As an evidence of rich vocabulary, there are about 50,000 entries and subentries of words in Bangla lexicons (Ali 1995). Like any other major languages, it is in a process of adopting many words from Arabic, Persian, Urdu, Turkish, English and others. After adoption, those foreign words mostly follow the phonetic characteristics of Bangla (Haq 2004). In this study, Bangla alphabets are written in Bangla scripts and, for universal readability and pronunciation cues, International Phonetic Alphabet 3 CHAPTER 1. INTRODUCTION (IPA, revised version of 2015) is used side-by-side for all phonetic transcriptions in this study (IPA Chart 2015). This study is related to any mosque for Bangla speaking community in the world. However, mosques of Bangladesh have been cited to give examples in discussions. This is because, Bangladesh has 90.4% Muslims of its huge population of 149.8 million (Report on Population Census 2011). To serve this large community, there are about 250,400 mosques around the country (Masjid Jorip 2008). This makes the mosque as one of the most common building type in Bangladesh. The architectural design of Bangladeshi mosques follows local features of the warm-humid climate of the sub-tropic, building materials and construction system. A mosque is basically a large hall room having almost no furniture. It is usually clad with finish materials of low absorption. As a sacred worship space, it is naturally calm and quiet.