Aciustics challenges in mosque

Abstract

The importance of mosque acoustics has long been realized. The importance of mosque acoustics in terms of clarity of speech is very essential. Besides the cleanliness, spaciousness, serenity in mosques that are required by the congregation to perform prayers and other religious rituals, Friday sermon and lectures are important speech activities in mosques. Through these activities, the congregation will be hearing messages of reminder of their religious and social duties. Famous mosques in Turkey built by Architect Sinan (1489- 1578), namely the Blue mosque in Istanbul and Shehzade Mosque in Ankara, are known to have an excellent acoustic quality, even though the interior of the mosques appear to be very reflective. It was reported that Architect Sinan had achieved suitable acoustic quality in his masterpieces through various approach such as the so called Helmhortz resonators, carved surfaces and specially blended materials to provide proper absorption of sound (Turkish Airlines In-flight Magazines, 1988). The mosque functions and activities basically involved speech, primarily sermon during Friday prayer, group lecture and seminars. As such, achieving optimum speech intelligibility should be the main acoustics design criteria. In Malaysia, this requirement has not been properly met as it has been voiced by the congregations, particularly during the Friday sermon, prayers and during group lectures. Also the structure of words in the Malay language is quite different from those of the English’s. Words in Bahasa Malaysia basically consist of two syllables, whereas, one syllables is common in English language. Optimum reverberation time requirement intended for achieving acceptable speech intelligibility for the language used should be the main acoustics criteria that need to be looked into. Equal distribution of sound level and optimum sound reflections affect acoustics in mosques. Sound level (SPL) is measured in decibel (dB). Consistent SPL is sought for in the main prayer area of a mosque. Significant variation of SPL level that is more than 5dB from one point to the other in the main payer area should be eliminated. The amount of time for a word sound to decay and unheard is measured by the reverberation time (RT60). RT60 is affected by the room volume and average of sound absorption of finishes of the room. If RT60 is too low, the syllable will be lost before it reaches the listener. On the other hand, if RT60 is too high, the incoming syllable of a word will be polluted by the previous syllable of the word. The word will get mixed up, and thus reduce the clarity of speech. This chapter describes the possible use of ventilation walls, a common building feature in hot humid Malaysia, as a mean of achieving consistent SPL and acceptable RT60 which will lead to achieving optimum speech intelligibility.