Evolution of a concert hall: Lateral reflections and the acoustical design for Wellington Town Hall

Abstract

The evolution of research and acoustical design objectives which have been the basis for the preliminary design phase of the Wellington (NZ) Town Hall is reported. The undoubted success Christchurch Town Hall with four years of evaluation in intensive use, and with the progress of research together indicated the acoustical refinements and modifications to be included in the Wellington Town Hall design. There has become a growing recognition of the fact that the directional properties of early reflections are as important in the perception of sound in concert halls as their temporal distribution. Marshall's early papers on the importance of lateral reflections led to a comprehensive study on the effects of early reflections on subjective acoustical quality in concert halls by M. F. E Barron at Southampton. The study includes details of masking of both high‐ and low‐frequency orchestral sound in lateral reflections, integration time, quantitative prediction of “Spatial Impression,” image shifting, and the difference limen. Results of other studies are presented which give complementary results in listener preference for relative levels of lateral and frontal energy. While model studies and in situ evaluation have shown that conventionally fan‐shaped halls cannot usually provide the preferred levels of envelopmental energy, acoustical experience in Christchurch has shown that in halls of this type, the preferred relative levels of lateral sound are achievable. Specific design features are presented including the use of longitudinally oriented “Quadratic Residue Diffusers” which provide multiple lateral reflections. The result is an unpresidented design proposal.