Acoustic quality assessment at Nezamol molk dome of Jame mosque of Isfahan

 Incontrovertibly, the sense of hearing is one of the five most substantial human senses. In fact, the human ear receives sound and transmits to the human brain by the auditory organs. Hence, sound can be considered as one of the key tools of human communication with each other and the environment around them. Since acoustic has a profound impact on the body, soul, and the performance of human it finds a unique place in cooperation with other sciences, namely architecture, in itschr('39') hundred years of existence. In accordance with this issue, one of those spaces that has a great impact on the level of performance, and sense of serenity is mosque. This is because individuals gather together in mosques in order to find a quite space away from everyday conflicts. In the past due to lack of cutting-edge technology, there were some predicament for people inside the mosque to hear the voice of speaker; however, mosques were designed in a way to have a great acoustic response on the environment. Actually the high volume of space and the large number of hard and reflective materials, somehow made it difficult for the audience to understand speech and sound. Geometric decoding of the architecture of Iranian mosques from the perspective of engineering and understanding the effective parameters of the capabilities of structures and their performance are the requirements that should be considered in order to preserve and revive these works and their application in contemporary architecture. One of the most unknown functionality features of mosques, especially in domes, are their sound status which according to contemporary knowledge does not have comprehensible engineering and even has some inconsistencies. Speech clarity and reverberation time are the main acoustic parameters of architecture that can be considered as indexes to examine audio comfort that have been influenced by a factor called geometry in the architecture of domes. In this research, jame mosque of Isfahan has been selected because it was a center of old texture of this city at the beginning of its formation at the second century AH which encompasses thousands of years of valuable structural, architectural, and artistic characteristics. The Nezam Al molk dome which is located on the south of jame mosque belongs to Saljuk era is one of the precious mementos with covered interior space decorated with break, stucco, stone, tile has been evaluated as one of the most prominent brick domes in terms of geometry and sound effects. Among the large number of studies and researches that are done in the world a very small percentage of it belongs to the acoustic science and especially the acoustics of mosques. While in this quantitative research with the help of simulation and accurate calculations of Ease 4.4 software which is one of the widely used applications in acoustic field, and according to the international standards presented in Acoustic books analyze the quality of sound and acoustic parameters in the dome the factors including reverberation time (RT), sound clarity (C50), speech transfer coefficient (STI), and audio pressure level (SPL) have been evaluated. The results show that acoustic parameters (RT is the most important) are not acceptable in the dome and need to be optimized, and owing to the fact that geometry and physical structure is inconvertible, optimization can be achieved by focusing on available materials. In contrast, Speech resolution (C50) in this space is appropriate and acceptable. In other words, mogharnas, squinches and all the introduced spaces in this model create a space that despite the inability to create an appropriate time reverberation, provides the required clarity of speech of the space. This contradictions, indicates the coordination of the components of the dome such as height, volume, squinch and Mogharnas and their effect on sound quality. In other words, transmission of sound to the upper space and exiting out of the level of the human ear as well as absorption of sound energy will assist to broadcast sound greatly and create clear audio in the space itself. As a consequence, the effect of background sound from external environments will be minimized in order to provide understandability and clarity of speech in the dome. Geometry and applied materials at the dome were designed to broadcast the sound, more reflection and stability of the sound in the atmosphere, and it is not focused on clarity of the sound. Perhaps the goal of the space designer is to enhance the sense of place by using sounds, not verbal reminders, which are merely conveying meaning and content, and background sound (without semantic connection) creates a sense of space and place. Center, south, southwest, southeast, of dome have a better position in terms of acoustic. Certainly, the acoustic study in such an important historical building is a turning point for more knowledge of traditional Iranian architecture and its preservation and continuity based on the needs of the contemporary era.