تأثير ويژگي هاي فضايي در مناظر صوتي سراهاي بازار تبريز

The effects of spatial features on the Soundscapes of Khans of Tabriz Bazaar

شاخصه هاي متعددي در كيفيت منظر صوتي فضاهاي شهري مؤثر هستند كه رفتار آكوستيكي فضا، يكي از عوامل محيطي تأثيرگذار در منظر صوتي است. مؤلفه هاي متعددي در رفتار آكوستيكي مكان ها دخيل هستند كه فرم، مصالح و حجم فضا از مهمترين آنها به شمار ميرود. چگونگي اثرگذاري اين خصيصه ها در رفتار آكوستيكي سراهاي بازار بزرگ تبريز و بالتبع تأثير آن در آسايش صوتي و كيفيت مناظر صوتي سراها، مسئله اي است كه پژوهش پيش رو به آن مي پردازد. كيفيت منظر صوتي تا حد زيادي وابسته به آسايش صوتي است كه اين مسئله خود در رابطۀ مستقيم با تراز فشار صوت فضا قرار ميگيرد. در اين راستا، تراز فشار صوت به عنوان مؤلفه پايه در اين تحقيق در فضاهاي مورد مطالعه، سنجش و اندازه گيري ميشود. سه سرا با حجم بزرگ، ميانه و كوچك از سراهاي بازار تبريز به عنوان نمونه هاي مورد مطالعه انتخاب شده اند كه به ترتيب عبارت هستند از سراي حاج حسين مياني، سراي حاج حسين قديم و سراي ميرزا محمد. در هر سرا، چهار نقطۀ محوري و يك نقطۀ مركزي به عنوان كانونهاي اندازه گيري مشخص شدهاند. در هر پنج نقطه، برداشته اي يك دقيقه اي با دوربين آكوستيكي انجام شده كه نمودار اسپكتروم اين برداشت ها نمايانگر تراز فشار صوت به تفكيك فركانس ها است. ميانگين مقادير تراز فشار صوت در سه حالت كمترين، ميانه و بيشترين محاسبه و برآيند اين مقادير ميانگين، به صورت كلي براي هر سرا در قالب نموداري ترسيم شده است. از مقايسۀ تطبيقي نمودارهاي برآيند مقادير ميانگين تراز فشار صوت در سه حالت، چنين نتيجه گيري مي شود كه به رغم تفاوت در اندازۀ حجم سه سراي مورد مطالعه، اين فضاها رفتار آكوستيكي مشابهي از خود بروز ميدهند. رفتار هر سه سراي ميرزا محمد، حاج حسين قديم و مياني در جهت تضعيف امواج صوتي، خصوصاً اصوات بم بوده است. از طرفي تمامي مقادير اندازه‌گيريشده در محدودۀ شنوايي انسان و آسايش صوتي قرار دارند. به بياني ديگر، طراحي معماري و شهري سنتي كه به خلق بازار تبريز منجر شده، در كنار توجه به مؤلفه هاي بصري و فضايي، در جهت تأمين آسايش صوتي نيز كارا است.

There are numerous affecting indices on the quality of urban soundscape and sonic comfort is the most important among them. There are several components involved in the acoustic behavior of places, the most important of which are the form, materials and volume of the space. How these characteristics affect the acoustic behavior of the Sarâs of Tabriz Grand Bazaar and consequently its effect on the sonic comfort and quality of the soundscapes of these spaces is the issue that the present study addresses. The quality of the soundscape depends to a large extent on the sonic comfort, which is directly related to the Sound Pressure Level (SPL) of the space. Sonic comfort is directly related to the Sound Pressure Level as well as acoustic behavior of the area and intensive sound produced by the sound sources. Basic affecting components on the acoustic behavior of an area are: parametric features, form, and volume of the area. In this regard, the Sound Pressure Level as a basic component in this research in the studied spaces has been measured. The aim of this paper is to demonstrate how the mentioned indices are affecting acoustic behavior of Sarâs of Grand Bazaar of Tabriz as well as sonic comfort of the Sarâs. Three Sarâs with large, medium and small volume of Tabriz Bazaar Sarâs were selected as the case studies. These spaces are Middle Haj Hossein Sarâ with high volume, Old Haj Hossein Sarâ with medium volume and Mirza Mohammad Sarâ with low volume. Volume difference of the three khans is the same. Volume of small Sarâ is 6000 cubic meter smaller than that of the middle Sarâ; also, the large Sarâ is the same amount larger than that of the middle one. In each Sarâ, five points have been selected to measure the Sound Pressure Level. These five points are the four axial points and a central point that are designated as the focal points of the measurement. At each of the five points, one-minute shots were taken with an Acoustic Camera. One of the outputs of the acoustic camera is the Spectrum Diagram. This diagram shows the Sound Pressure Level by frequency. In addition to the spectrum diagram, the acoustic camera provides output Sound Pressure Level values by frequency in tabular form. Using the precise details of the Sound Pressure Level at each point of measurement, the average values of the Sound Pressure Level in the three modes of minimum, middle and maximum were calculated. The result of these mean values was then plotted for each Sarâ in the form of a graph. According to the comparative study of the diagram, it was concluded that although parametric indices were different acoustic behavior of the three Sarâs were the same. The acoustical behaviors of all three Sarâs of Mirza Mohammad, Middle and Old Haj Hossein have been to weaken the sound waves, especially the bass sounds. Also, all measured SPL values are in the range of human hearing and sonic comfort. In other words, the traditional architectural and urban design that has led to the creation of Tabriz Bazaar, in addition to paying attention to the visual and spatial components, is also effective in providing sonic comfort.