Sound insulation

Abstract

For most roofs, minimum deadweight is an important criterion of design. Light insulated decks, or thin membranes, are therefore almost universal on long spans. This requirement is in conflict with the need for heavy mass for the reduction of sound transmission. In many long-span factories, stadia and hangars, internal noise levels are so high that reduction of external noise is unnecessary. On the other hand adequate sound reduction through the roofs of auditoria and concert halls is of paramount importance, and they are increasingly affected by overhead noise from aircraft. An outer concrete membrane of adequate thickness may be associated with an inner, structurally isolated shell, or a heavy ceiling suspended from hangers of minimum cross section, to provide sound reduction. The depth of the interspace and its lining with acoustic absorbents can thus be important factors.