Sounds in the Rounds

Abstract

Architects and engineers utilizing thin shell concrete domes, space frames of compound curvatures, and circular plan forms to enclose monumental spaces have created some of the most imaginative structures of our day. It would seem that the aesthetic possibilities and structural economies are unlimited. However, acoustical analyses performed on some of the structures indicate that serious acoustical defects can occur, if proper precautions are not taken. This paper presents a discussion of the fundamental problems inherent in these forms which give rise to the acoustical phenomena known as creep, focusing, and flutter echoes. For example, recordings in some of the recently completed structures indicate that prior to corrective acoustical treatment, flutter echoes may persist for periods in excess of eight seconds. The use of design studies to predict and control these phenomena is described and tape recordings are presented as an audio presentation. Experience gained from studies of these structures indicates that several basic techniques employing the use of sound reflecting and/or sound absorbing materials can produce aesthetically pleasing results as well as a satisfactory acoustical environment.