Experimental Investigation About the Influence of the Use of Glue in Joints in Lightweight Structures

Abstract eng:
Lightweight timber structures have many advantages, but high-demand acoustic quality is hard to achieve due to the relatively poor insulation through the junctions, especially in the low frequency range (20 Hz-200 Hz) where the weight (mass per unit of area) of a construction is an important parameter for the air-borne insulation properties [1]. Increasing the mass would improve the insulation but this would go against the main advantage of lightweight constructions. Impact sound from a walking person is the most common sound insulation problem for these kinds of structures, where the footsteps produce a high-degree of noise disturbance. Similar investigations of junctions have been done before [2]. The aim of this particular investigation, however, is to show how glue modifies the sound transmission through the joints in a wooden floor. Theory shows that coupling occurs in a joint either along a line or at individual points depending on the distance between the screws or nails with regard to the bending wavelength [3], [4]. When a viscous elastic material as glue is inserted in between the parts of the joint, the behavior will change and it is therefore important to be studied. To achieve this aim, two structures were built. The first one constituted of two squared plates of dimension 0.6 m x 0.6 m, each one of them fixed onto one beam 4.5 m wide and 22 cm high, by means of equidistant screws. A second set-up was built too, but this time only a single 1.2 m x 0.6 m plate was fixed onto the beam. The same structures were built again a second time, but this time glue was applied around the screws on the contact surfaces.

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