The Acoustical Performance Analysis of Bilkent Amphitheater: Proposal for Acoustical Renovation

Abstract

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 sufficient 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, clarity, definition, lateral fraction, strength and speech transmission index were calculated by the aid of ODEON Room Acoustics Program simulation software Version 6.01. It was observed that most of the parameters are out of the optimum range, and that the sound focused strongly in some locations. After further acoustical renovation of the hall, the distribution of sound became more homogenous as measures of most of the parameters fell into reasonable ranges.