The increase in industrial life in today's societies has caused much noise damage, and reducing noise in residential, office, and industrial environments has become a daily challenge. In this regard, the use of soundproofing / absorbing materials is one of the effective and economical solutions for significantly reducing the noise of industrial equipment. In this study, 34 experimental tests were conducted to evaluate the effect of five different insulators on reducing the sound intensity passing through two aluminium hemispheres and cylinder chambers. The five insulations include polyethylene, EVA, polyurethane, felt, and fiberglass, which were examined in three thicknesses of one, two, and three layers. The results of the evaluations showed that the most effective insulation materials among the five selected materials were felt and fiberglass. According to the results, the ability of felt and fiberglass to absorb sound energy, increases from about 10 and 8% (1-layer) to about 40 and 38% (3-layers) respectively through frequencies of 250 to 16000 Hz.
Najafi et al. (2025) studied this question.