Requirements for successful concert hall design: Need for lateral and ensemble reflections

The Plan-form chosen for a concert hall ("Shoebox", Fan, Areana, etc.) is an important but secondary factor in the design of a successful hall. To be acoustically successful the room must enhance the musical experience of the listener, whether on stage as a performer or in the audience. For each of these two situations (which have quite different specific requirements) the primary design objective is to produce by the design of the room the appropriate sound fields for enhancement, at the listener\´s head. Today after two decades of research the preferred acoustical conditions for both performers and audience are known in terms of the physical properties of sound fields and their architectural correlates. There is no longer any need for the designer to accept doctrinaire views on any one room shape from the acoustician, or indeed unarguable pronouncements more appropriate to magic than acoustics. The new knowledge is available in an architecturally meaningful way which is accessible, and frees the designer while constraining the design. Acoustical solutions are geometrically impossible in some room shapes, but the reasons why are explicit. In this paper we establish these views by reviewing the development of knowledge on the preferred acoustical conditions during the past two decades. We include a discussion of the first two halls designed on this basis and on which one of the authors was consultant. One of them, the Perth Concert Hall is classical in shape. The other, Christchurch Town Hall, is radical yet both had the same design objectives. They illustrate the freedom which follows this first principles approach.