Development of an equivalent solid model to predict the vibroacoustic behaviour of earmuff cushions
AbstractA study that examines the relevance of using an equivalent isotropic visco-elastic solid model to capture the sound transmission law of an annular cushion from a commercial earmuff is presented. Ten cushions from a hygienic spare set are studied. They are mounted on a shaker and submitted to the weight of three metal blocks with masses of 1.15kg, 1.65kg and 2.13 kg, representing the force applied by the head band when the earmuffs are positioned on the head. Holes are glued with cyanoacrylate glue, when each cushion was under compression, to evacuate air from it. Vibration experiments were conducted and then cushions were immerged into water to make sure that apertures were completely occluded. Such verification has demonstrated that the sheath is a micro-porous material: micro air bubbles appear around the sheath when cushion are pressed. The foam and the sheath are tested separately under a mass of 0.65kg and compared to a cushion.
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