Experimental Researches on the Sound Absorption Composites Used for Public Worket Equipment

Abstract

Decreasing of sound and vibration global level inside and/or outside the public works equipment’s cabin as well as the reduction the noise pollution or the pollution accounted by the vibration and mechanical shocks on the construction site is an actual matter, especially for the countries having become lately EU members; these countries must harmonize their national legislations regarding the environment pollution and the labor protection according to the EU Directives (98/37/EC, 2000/14/EC, 89/391/EEC, 2003/10/EC, 89/656/EEC, 92/85/EEC). This study presents the problem of designing, manufacturing and testing of some protective systems made of composite materials which can simultaneously perform the next requirements: noise absorption for middle and high range frequencies (400-8000 Hz), noise insulation for low frequencies (40- 400 Hz), vibration damping in order to avoid noise transmission by structure and finally, modularity and adaptability for using to different types of public works equipment, also for other technological equipment with a high level of noise, vibration and mechanical shocks. This article presents the experimental data of sixteen composite structures with noise absorption and insulation features and one case study of global level noise reduction L inside the cabin of a crawler excavator. The experimental research has done with Brüel & Kjær acoustic measuring equipment at the Vibration and Acoustic Laboratory of the Research Institute for Construction Equipment and Technology - ICECON S.A. Bucharest, Romania. The study case for the excavator S1021 was made in the Research Center of Machines, Mechanic and Technological Equipments – MECMET from "Dunarea de Jos" University of Galati, Engineering Faculty of Braila.