Studies of sound absorption and sound transmission loss of hemp shives

Abstract

Taking into account global sustainability trends, synthetic sound-absorbing materials are increasingly being replaced by natural materials. One such material is hemp fiber. Although hemp fibers and shives are quite well researched worldwide, scientists emphasize the need for research tailored to each region where hemp fibers are grown, as their properties vary greatly due to environmental conditions in different growing locations. The aim of this study is to investigate the sound absorption and sound insulation properties of hemp shives, shive and fiber mixtures, and shive blocks grown in Lithuania, and their dependence on the thickness and density of the samples tested. Experimental studies are conducted following standard methods ISO 10534-2 and ASTM E2611-17. It has been found that samples of thicker hemp shives and hemp shives with fiber better absorb sound at medium and low frequencies. Samples with a density of 150 kg/m3 generally absorb sound better across the entire frequency range compared to samples of the same thickness but with a density of 100 kg/m3. Mixing hemp shives with decorticated hemp fiber improved sound absorption across the entire frequency band.