Experimental tests and prediction of insertion loss for cubical sound insulating enclosures with single homogeneous walls

Abstract

Limiting the excessive noise of machines and devices can be performed with the use of screens in the form of baffles or acoustic enclosures. Knowledge of their acoustic properties is essential in the proper construction of baffles. The basic properties include the airborne sound insulation of the baffle, and the insertion loss in the case of the arrangement of several baffles constituting the acoustic enclosure. Both parameters can be determined through experimental tests, including laboratory ones and using theoretical computational models.The article presents the results of both experimental and model tests of the sound insulating effectiveness of enclosures. The proposed calculation model for the insertion loss of sound insulating enclosures, intended for mid- and high-frequency ranges, was determined on the basis of the sound transmission loss of a homogeneous baffle, which was calculated from its material data using a theoretical model developed within previous studies, based on the Davy and Sharp models. For the low-frequency range, the use of a modified Oldham model for close-fitting enclosures was proposed. The new calculation model was validated for six enclosure variants consisting of five identical square plates, made of materials such as steel, aluminium, plexiglass, polypropylene and gypsum. For this purpose, the developed prototype stand for testing acoustic enclosures was used, with the possibility of mounting walls of different thickness. A good correlation between the results of the insertion loss spectral characteristic calculations and the results from experimental tests was obtained using the proposed model, in the entire considered frequency range of 100–5000 Hz.