Calculating the Acoustical Properties of Plane Uniform Constructions

Abstract

A procedure for calculating the measures of the acoustical performance of a wide range of plane acoustical constructions which are used in buildings and in industry is described. These measures include the sound absorption coefficients, the sound reduction indices, and the sound insertion losses in 1/3 octave bands for a diffuse field incident upon the construction. The calculation procedure exploits the fact that a wide range of architectural and industrial acoustical constructions is formed from relatively few layer types. Common layer types are an impervious sheet, a layer of porous material, and an air-space. These layer types can be used to form absorbers, partitions, and laggings. Formulas which relate the wave impedances and the acoustic pressures on the opposite sides of the various layer types are developed and the method of combining these impedance and pressure formulas so that the appropriate measures of performance of multilayer constructions can be calculated is described. Comparisons between the calculated and the measured performance measures for a number of different constructions are used to demonstrate the value of the procedure.