This research investigates the acoustical characteristics of mosques of the classical Ottoman period and the contemporary period. Kocatepe Mosque, the major mosque in Ankara, Turkey, as a case from the contemporary era is a unique combination of 16 th century Ottoman aesthetics and 20 th century technology. Although previous and recent mosques have been inspired by this combination, the use of a reinforced concrete dome without cavity resonators could cause long reverberation times especially in low frequencies. The purpose of this study was to investigate this condition by studying Kocatepe Mosque. The acoustical characteristics of the mosque were analyzed by computer simulation. Objective room-acoustic indicators including reverberation time (RT), early decay time (EDT), clarity (C80), definition (D50), lateral fraction (LF), speech transmission index (STI) and strength (G) are presented. The results show that the acoustical quality of Kocatepe Mosque is not optimal when it is empty, and closest to optimal conditions when fully occupied. The new techniques to overcome excessive low frequency attenuation caused by huge concrete shells of today's mosques are discussed in conclusion.
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The user has requested enhancement of the downloaded file.Keywords: Room acoustics, Acoustical parameters, Acoustical simulation, Acoustical design, Multi-purpose hall, Room acoustics. © 2006 University of Sydney. All rights reserved. Architectural Science ReviewVolume 49.2, pp 167-178 www.arch.usyd.edu.au/asr *Department of Interior Architecture and Environmental Design, Bilkent University, 06800 Bilkent, Ankara, Turkey †Corresponding author. Tel.:+90-0312-290 2592; Fax: +90-0312-266 4136 E-mail:semiha@bilkent.edu.tr IntroductionOne of the main goals of architectural acoustics in the case of multipurpose auditorium, which is the gathering place for speech and music performances, is to provide both the optimum speech intelligibility and the sound quality [1,2]. The greatest challenge that the designer confronts at this point is to accommodate both unamplifi ed music and unassisted speech within the same place, which is especially much diffi cult for the halls with seating capacities exceeding 2000 or circular in form as in the case of Bilkent Amphitheater [3,4,5]. The Acoustical Performance Analysis of Bilkent Amphitheater: Proposal for Acoustical RenovationThe Amphitheater with 4000 seating capacity was designed to serve the university's and the city's educational and artistic activities, which are comprising both the music and speech performances including concerts, operas, dance and stand-up shows, theaters, conferences and graduate ceremonies. The Amphitheatre's architecture, while reminiscent of a classical Roman amphitheater, highlights the features of high technology with its steel structure roof covered by a textile membrane, besides glass and a cable network system. Consequently, the architectural form is a synthesis of two architectural styles separated by 2000 years. "Both in terms of its original form and dimensions, and the combined use of three different modern load bearing structures, Bilkent Amphitheater is the fi rst of its kind" [6]. Although, the form and the synthesis of architectural styles results in an innovative building typology, the same reasons lead to a problematic acoustical space. The purpose of this paper is to determine The 4000 seat multi-purpose Bilkent Amphitheater is a semi-closed amphitheater with a volume of 90,000 m³, designed to serve the University's and the city's educational and artistic activities. At the beginning, the amphitheater was designed only for open-air performances. Afterwards it was decided it would be roofed with a tensile membrane in order to protect the spectators from atmospheric effects. However, the covered amphitheater was turned into a resounding and a problematic place with a reverberation time of more than 6 s. when the hall is unoccupied. Acoustical interventions were implemented, but these have not been suffi cient in decreasing the number of problematic echoes and dead spots. This paper analyzes the hall by means of assessing the fundamental acoustical parameters for both speech and music. Parameters such as reverberation time, early decay time...
Recently, architectural acousticians have been increasingly interested in halls that incorporate coupled-volume systems because of their potential for creating nonexponential sound energy decay. Effects of coupling-aperture configuration and source and receiver locations on energy decay are essential aspects of acoustically coupled spaces that have not yet been extensively investigated. In order to further understand these effects on sound fields in coupled rooms, a systematic experimental study is carried out. An acoustic scale model technique is used in collecting room impulse responses of a two-room coupled system for varying aperture configurations and surface-scattering conditions. Baseline behavior is established by varying aperture area for a fixed aperture shape and analyzing relevant energy-decay parameters at different locations. Effects of aperture shape and number are systematically investigated by varying these parameters while holding coupling area fixed. Similarly, effects of receiver location are systematically investigated by varying the distance of the receiver from the coupling aperture for a fixed aperture configuration. Schroeder decay-function decompositions by Bayesian analysis reveal sensitivities to receiver location and aperture configuration across different frequency bands.
As a case study, this work aims to experiment coupled-volume systems with scientifically grounded quantifiers using Bayesian analysis, a reliable analysis method in evaluating effects of different parameters on sound energy decays of coupled rooms [Xiang & Goggans, J. Acoust. Soc. Am. 110, 1415 - 1424 (2001)]. This research uses the well-defined indicators developed by Xiang and Goggans to assess sound energy decays in a real-size hall. Derived from the model-based Bayesian inference, level differences (ΔL), diverse decay times, and decay time ratios are the quantitative descriptors of sound energy decays in acoustically coupled spaces. The room impulse responses of Howorth Theater in Oxford, Mississippi coupled to the adjacent lobby are experimentally measured in the case study. The two rooms are connected with two separate apertures and have distinct natural reverberation times that allow experimenting different setups for probable acoustical coupling at certain locations. In this paper, frequency, and location dependence of double-slope characteristics of sound energy decays are discussed.
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