Influence of Acoustic Data in Architectural Design

One of the small mahfills in Suleymaniye Mosque

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The results of our investigation to define acoustic properties of Sinan's mosques proved the abundance of his knowledge and applied technology on acoustics and his ability in utilising them in architectural design. Especially, the obtained data from mosques other than his two large ones supports this view. Although the measured reverberation times of Suleymaniye and Selimiye were quite reasonable at middle and high frequencies, there were serious problems at low frequencies. The basic reason for such results is the mistakes that were made during the restoration activities without having sufficient knowledge of the applied technology. On the other hand, because of the size of Sinan's two big mosques, the delayed reflections have negative effect at those frequencies. On the other hand, the existence of muezzin mahfil (a gallery for the cal to prayer) in different locations in all three mosques is considered important; although a small mahfil was added on to two pillars at the back of the Suleymaniye, it was not desired in the Selimiye. The data led us to analyze the plan graphics of the three big mosques again; the analysis showed us improvement on Sinan's acoustical concept during their design process and also his awareness of the intelligibility problem. It has been determined that, with this awareness, Sinan began to search for a solution to get sufficient intelligibility and he combined architectural design with acoustic design. The data given below led us to these results;

Table 1. Maximum room volume according to type of sound source within

First of all, the calculations of the interior volume of all three mosques show us that there is a lack of sound power due to sound sources in the mosques. The maximum volumes of the rooms are given in Table 1. The Shehzade Mehmet Mosque, in spite of being the smallest of the three mosques, has an interior volume of almost 50,000 m³. Looking at Table 1, we can see that only massed choirs can produce the sufficient sound power for the room with that size of interior volume. The muezzin's mahfil in this mosque is located next to the northwest pillar. It is evident that although there are cavity resonators in the dome, the sound energy will remain insufficient and the total sound energy of those working at the muezzin's mahfil will not be the equivalent of large choirs.

The Acoustic Space and the muezzin's mahfil in the Suleymaniye Mosque

It is realized that besides enlarging the interior volume of the Suleymaniye Mosque even more, Sinan tried to increase sound power by a number of sources. For this purpose, he placed the muezzin's mahfil near the mihrab, next to the southwest pillar and in addition, he added small mahfils (balconies) to the two north pillars. The data show awareness of the need for extra sound power during the design process of this mosque with interior volume approximately 88,000 m and the data also demonstrate the greatness of both the period's and Sinan's acoustic knowledge. It must be noted here, however, that there is also a lack of knowledge in this application. In such a large enclosed volume having more than one source located at different places and with the repetition of the sounds from the first and following sources naturally create duplicate sounds or even multiple sounds resulting in unintelligible sound or noise.

For the Selimiye Mosque in Edirne, it is evident that Sinan made an effort to achieve a reasonable solution to the acoustic problem. For this purpose, he designed a total space for the interior of the mosque, not divided into spaces and reduced to the size of room. The interior volume of the Selimiye Mosque is approximately 75,000 m³ and, naturally, it is evident that the problem of the power of the sound source will arise. To overcome this problem, Sinan placed the muezzin's mahfil exactly in the centre of the total space. The dome and also cavity resonators are directly above the sound source. The resonator system that will diffuse the sound energy into the room, being close and having no effect of reflected sound, will take the sound energy directly from the source and diffuse it throughout the entire room. Here intelligence shows its creativity, and for the first time in the history of civilization, we encounter an acoustic space. The sound energy coming from above defines a space - an acoustic space. It must be remembered that for Sinan's design there is no application without a reason.

For many years, historians have sought the answer to the question "after creating a total space, why did he put the muezzin's mahfil right in the centre".

Now we can easily say; "The answer is to create an acoustic space".

by: FSTC Ltd