For a mosque in Bangladesh, the acoustical requirements in terms of intelligibility and liveliness are dissimilar for the types of sounds - recitation from the Holy Koran and speech on religious subjects. To attain an overall satisfactory acoustical performance, it is significant to find an optimum Reverberation Time (RT), which is one of the important factors affecting intelligibility and liveliness. Experiment is conducted to find the effect of RT by making it a variable, while keeping other factors as non-variable and fulfilling ideal conditions for maximum intelligibility. Preferences are judged on pairs of sound clips of recitation and speech, for both intelligibility and liveliness, on a 5-point scale and findings are analysed thorough the statistical method of paired comparison. Considering preferences of all aspects the optimum RT is proposed as 0.9 s for an overall balanced acoustical performance for both recitation and speech for a mosque in Bangladesh. Keywords: Intelligibility, Liveliness, Mosque, Recitation, Reverberation time, Speech.     DOI: 10.3329/bjsir.v44i2.3667 Bangladesh J. Sci. Ind. Res. 44(2), 163-170, 2009

A mosque facilitates a Muslim community through different religious activities like congregational prayers, recitation and theological education. Speech in a mosque usually generates through bare voice though sound amplification system is also applied. Since no musical instrument is used in any liturgy, a mosque involves only speech acoustics. The community mosques of Dhaka city, the densely populated capital of Bangladesh, are usually designed and constructed by common people inspired from religious virtues. Seeking consultancy for acoustical design is almost never done. As an obvious consequence, there is a common crisis of speech intelligibility in different mosques, except those saved for their smaller volume and other parameters generated by chance. In a very few cases, a trial and error method is applied to solve the problem. But in most of the cases, the problem remains unsolved, putting the devotees in endless sufferings. This paper identifies the type and magnitudes of the prevailing crisis of speech intelligibility of these community mosques through instrumental measurements and questionnaire survey. This paper is also intended to establish certain research rationale and hypothesis for further research, which will propose certain parameters in acoustical design for mosques of Dhaka city in particular and of Bangladesh in general.

A comfortable acoustical environment is imperative for the safety, well-being and recovery of patients receiving treatment in any type of healthcare service. Unfortunately, lack of satisfactory acoustical performance in most healthcare buildings worldwide has led to unfavorable prevailing conditions such as extremely noisy environment, irritation, disturbance, deterioration of a patient's health, and increase in likelihood of being readmitted into hospitals. This paper presents a case study on a diagnostic clinic targeted for autistic individuals in Mohammedpur, Dhaka as an attempt to investigate prevailing conditions of acoustical performance in healthcare facilities of Dhaka city. Questionnaire survey on users, instrumental survey on background noise levels and observations were conducted to obtain quantitative and qualitative data on acoustical performance. Instrumental survey results indicate that noise levels inside the specified clinic ranged from 59.5 to 76.5 dBA -exceeding the allowable limits of local and international standards. Questionnaire survey results also signify users' dissatisfaction with existing noise conditions and thus a poor acoustical environment. This study is expected to develop awareness on current unacceptable acoustical conditions of healthcare facilities and provide tentative propositions to commence effective initiatives for developing design criteria for healthcare buildings in general, and those for autistic group in particular.