Functions for noise reduction in acoustic standards: evaluating reverberation time, mean absorption coefficient, and a novel approach

Abstract

Contemporary European acoustic standards utilize dimensioning functions based on either reverberation time or mean absorption coefficient. For spaces with the primary goal of noise reduction, achieving consistent overall sound pressure level (SPL) reduction, regardless of room sizes and shapes is evidently desirable. The conditions under which reverberation time and mean absorption coefficient approaches align with the objective of consistent SPL reduction are analyzed. Generally, both approaches fall short of achieving consistency in case of varying ground surface or room shape, i.e. length, width and height relations. Additionally, in large rooms, constant or room height-dependent reverberation time functions may lead to extensive absorption areas, complicating the installation of acoustical treatments and degrading their economic efficiency. A novel dimensioning function, providing consistent SPL reduction independently of room size and shape, is derived based on diffuse field theory. The novel function is multiplied by a linear function of room height and length, to alleviate accuracy limitations of diffuse field theory in case of varying room shapes. Finally, simulations systematically varying room sizes and shapes demonstrate that the novel dimensioning function significantly outperforms existing approaches in achieving consistent SPL reduction.