The importance and feasibility of “Reflectivity” as an index applicable for architectural acoustic design

Abstract

A major part of room acoustics concerns sound control within a space. This traditionally involves reverberation control, music envelopment, optimization of speech comprehension and privacy, noise control, spatial enhancement, modal and reflection control for rooms used in recording, mixing, editing, mastering, and measuring sounds and hearing. In all of these examples, room acoustics is influenced by early reflections from the interior surfaces, objects and geometry. The impedance of a surface generally varies in relation to the incident angle of sound waves, therefore knowing the true reflectivity of surfaces would be complimentary to sound decay time and absorption coefficients. This presentation reviews current trends in the measurement of sound reflectivity as well as many of the challenges involved in developing an approved laboratory measurement methodology. Not only a potentially important tool for acousticians, architects and designers, but a formally adopted “Reflectivity Index” would aid product design, research, and education in room acoustics. Examples of comparative measurements of materials ranging from porous media to continuous or perforated surface assemblies are examined and how the range of results might be unified as a single metric.