Browsing by Subject "Architectural acoustics"

Now showing 1 - 8 of 8

Open Access
Acoustical characterization of clay pots in Ottoman architecture through experimental and numerical analysis methods
(2022-07) Atay, Gülnihan
Employment of clay pots as building elements is a common practice especially in the medieval structures throughout Europe and Near East. Despite the fact that their acoustical employment in historic structures is well known and dates back to the 1st century BC as observed in Vitruvius' writings, their true contribution to the acoustics of Medieval Architecture remains to be a subject of discussion. They are also present in Ottoman Architecture including Süleymaniye Mosque designed by Sinan the Architect Laureate. Although these elements placed in the dome of Süleymaniye are often interpreted to be utilized as Helmholtz resonators, a scientific account regarding their sound-absorption performance is needed so as to understand whether they actually perform as cavity resonators. Therefore, the scientific investigation of their acoustical behaviour through analytical, experimental, and numerical analysis methods is necessitated. The objective of this study is to discuss the effects of the clay pots on the sound energy decay pattern of Süleymaniye Mosque. The study begins with an archival research phase covering the versatile employments of clay pots as building elements that are not limited to their acoustical utilization. The study then proceeds with the impedance tube measurements conducted with the reproduced sample of an actual-sized clay pot employed in the structure. The results are then verified with finite element modelling (FEM) simulations. Finally, sound absorption coefficients, obtained from the latter are transferred into the ray tracing simulations so as to understand the pots' effect on reverberation times (T30) in the edifice. In the conclusion part, sound absorption performance of clay pots and their possible contribution to the mosque acoustics are discussed. As a result of the study, the resonance frequency of the clay pots embedded into the central dome of Süleymaniye Mosque is found to be 50 Hz. Additionally, they are also proven to be effective at 500 Hz octave band. Consequently, the ray tracing simulations exhibit a 2 seconds decrease in T30 values at 500 Hz octave band. This also proves the improvement of reverberation time at this octave band range, which was measured after the final restorations of Süleymaniye Mosque with repaired pots.
Open Access
Acoustical design and noise control in metro stations: Case studies of the Ankara metro system
(2007) Sü, Z.; Çalíşkan, M.
The aim of this research is to demonstrate the importance of initial strategies in acoustical design of underground metro stations. The paper searches for practical design solutions by evaluating different materials for providing optimum acoustical conditions in such spaces. Acoustical designs of three metro stations on a new expansion line in Ankara including Sogutozu, Bilkent and ODTU metro stations are presented through computer simulation. Predictions of room acoustical parameters are presented for both platform and ticket office floors in terms of parameters like reverberation time (RT), speech transmission index (STI) and A-weighted sound level (SPL) distribution within spaces. Simulated reverberation times are evaluated in view of legislative requirements. The study confirms the importance of using sound absorbing materials on the ceiling and sidewalls together. The nonwoven material, used behind perforated metal suspended ceilings, has proved effective in reverberation control.
Open Access
Acoustical footprint of the traditional turkish baths in historic settings
(Taylor and Francis Group, 2023-04-20) Bora Özyurt, Z.; Sü Gül, Zühre
The Turkish bath structure (hamam) is one of the key typologies in Anatolian architecture. In addition to its main “bathing” function, Turkish baths are chosen as the main venue for social organizations in the Ottoman period, with eating and dancing accompanied by live music. Thus, the construction of baths, in various sizes, was prioritized then and still holds its place in the social and cultural life of Anatolia. This study investigates the authentic acoustical characteristics of Turkish baths, over four selected baths in Bursa, Turkey; Karamustafa (15th c.), Yeni Kaplıca (16th c.), Kaynarca (17th c.), and Tahirağa (19th c.). Room impulse responses are collected through acoustical field measurements. Acoustical simulations are utilized to experiment with the materials, which reflect the historical origins, as well as used to test the effects of different humidity levels on acoustical parameters. The objective parameter analysis includes EDT, T20, T30, C80, D50, and STI assessments. Relationships between objective parameters and geometrical attributes are investigated. Lower T30 and higher STI values are obtained with historical plaster in comparison to the up-to-date conditions. Controlled analysis in decreasing the relative humidity resulted in lower T20 and T30 values, consequently higher STI values. Obtained data are discussed considering the usage of male and female baths, traditional activities as well as the nature of the sound sources.
Open Access
A comparison study on sound defects of Bilkent Amphitheatre in terms of intelligibility of the speech
(2007) Yilmazer, S.
The 4000 seated multi-purpose hall Bilkent Amphitheater is a semi-closed amphitheater with a large volume of 90,000 m3.At the beginning, the amphitheater was designed only for open-air performances. Afterwards it was decided to be roofed with a tensile membrane in order to protect the spectators against atmospheric effects. However, the covered amphitheater was turned into a very resounding and a problematic place with a reverberation time even more than 6 s. when the hall is unoccupied. After that time, some acoustical interventions were implemented, but these have not been sufficient in decreasing the number of problematic areas of echoes and dead spots. In 2000, Akukon Oy Consulting Engineers, Finland, carried out the real-size measurements when the hall was unoccupied, in order to find out the values of different acoustical parameters. In 2004, the computer simulation of the hall for the unoccupied condition was made [2]. In order to test speech intelligibility in the hall, besides the computer simulation and real size measurements, in 2006, articulation testing (AI) was made by using normal hearing listeners in the hall. In this paper, comparison between the measurements and the experimental studies are presented. Results confirm that excessive values of reverberation time cause too much reverberant and liveliness throughout the hall, besides the lack of warmth subjectively. Clarity is undermined by excessive reverberate and the sound becomes blurred. Sound energy are not satisfactory in reflecting the sound sufficiently through the hall and the direct sound becomes insufficient at some locations as back and mid sides.
Open Access
Efficiency of sound energy decay analysis in auditoria
(Institute of Acoustics, 2023-09) Xiang, N.; Gül, Zühre Sü
Recent auditorium acoustics practice has included coupled-volume systems in several performing arts venues. This has stimulated research activities on acoustics in the coupled-volume systems. Based on experimentally measured room impulse responses acquired from existing auditoria, and several historically significant worship spaces, this paper addresses the challenges of analysing single-slope and multiple-slope sound energy decays often encountered in the experimentally measured room impulse responses in these venues. The analysis engages a parametric model of Schroeder decay functions, that decomposes the Schroeder decay data into single or multiple exponential decays along with a noise term. The model has been well validated using many experimental data. Several advanced analysis methods based on the decay model, such as nonlinear regressions, Bayesian probabilistic inference, and artificial neural networks have emerged to cope with analysis challenges raised in auditorium acoustics practice. This paper discusses conditions of implementing Schroeder integration for a higher efficiency of the numerical analysis and clarifies some unreasonable expectations/interpretations of Schroeder decay data. © 2023 Institute of Acoustics. All rights reserved.
Open Access
Matrix density effect on morphology of germanium nanocrystals embedded in silicon dioxide thin films
(Materials Research Society, 2011) Alagoz, A. S.; Genisel, M. F.; Foss, Steinar; Finstad, T. G.; Turan, R.
Flash type electronic memories are the preferred format in code storage at complex programs running on fast processors and larger media files in portable electronics due to fast write/read operations, long rewrite life, high density and low cost of fabrication. Scaling limitations of top-down fabrication approaches can be overcome in next generation flash memories by replacing continuous floating gate with array of nanocrystals. Germanium (Ge) is a good candidate for nanocrystal based flash memories due its small band gap. In this work, we present effect of silicon dioxide (SiO 2) host matrix density on Ge nanocrystals morphology. Low density Ge+SiO 2 layers are deposited between high density SiO 2 layers by using off-angle magnetron sputter deposition. After high temperature post-annealing, faceted and elongated Ge nanocrystals formation is observed in low density layers. Effects of Ge concentration and annealing temperature on nanocrystal morphology and mean size were investigated by using transmission electron microscopy. Positive correlation between stress development and nanocrystal size is observed at Raman spectroscopy measurements. We concluded that non-uniform stress distribution on nanocrystals during growth is responsible from faceted and elongated nanocrystal morphology.
Open Access
Perceived auditory environment in historic spaces of anatolian culture : a case study on Hacı Bayram mosque
(International Institute of Acoustics and Vibrations, 2016) Acun V.; Yilmazer, Semiha; Taherzadeh, P.
This article reports the initial finds of a research that is concerned with the perceived auditory environment within an historical mosque and its surroundings. Haci Bayram Mosque and its surrounding area of Hamamönü has been selected as the research site due to being the historical center of Ankara. Although there are studies concerned with the acoustical characteristics of mosques, there isn't enough research focusing on users' expectation and interpretation of the perceived auditory environment within a mosque. This study adopts the user focused of Grounded Theory to capture individuals' auditory sensation and interpretation of the perceived auditory environment within a historical mosque and its surroundings. In depth interviews are held with the congregation of the mosque and with the individuals sitting around the surrounding area. Based on their subjective responses, a theoretical framework is generated to gain an insight on the factors that affect individuals understanding and expectation from mosques. Acoustical characteristics of the mosque are analyzed by computer simulation and in-situ measurements of sound pressure levels. Objective room-acoustic indicators consist of reverberation time (RT) and speech transmission index (STI). The conceptual framework generated through Grounded Theory shows how perceived auditory environment may influence individuals' response to the physical environment of the mosque by showing the associations between the soundscape elements, spatial function and sense of place.
Open Access
Raman and TEM studies of Ge nanocrystal formation in SiOx: Ge/SiOx multilayers
(Wiley, 2007) Dana, Aykutlu; Aǧan, S.; Tokay, S.; Aydınlı, Atilla; Finstad, T. G.
Alternating germanosilicate-siliconoxide layers of 10-30 nm thickness were grown on Si substrates by plasma enhanced chemically vapor deposition (PECVD). The compositions of the grown films were determined by X-ray photoelectron spectroscopy measurements. The films were annealed at temperatures varying from 670 to 1000°C for 5 to 45 minutes under nitrogen atmosphere. High resolution cross section TEM images, electron diffraction and electron energy-loss spectroscopy as well as energy-dispersive X-ray analysis (EDAX) data confirm presence of Ge nanocrystals in each layer. The effect of annealing on the Ge nanocrystal formation in multilayers was investigated by Raman spectroscopy and Transmission Electron Microscopy (TEM). As the annealing temperature is raised to 850°C, single layer of Ge nanocrystals observed at lower annealing temperatures is transformed into a double layer with the smaller sized nanocrystals closer to the substrate SiO2 interface.