Investigation of Sound Absorption Coefficients of Coir Fibre Mat

Abstract

With the development of transportation sector, mitigation of the impact of transportation noise becomes major topic and various sound-absorbing materials and technologies have been developed and are widely applied across different modes of transportation. These materials help absorb, dampen, or isolate noise from the environment. The coir fibre mats and composites are identified as effective and eco-friendly sound absorbing materials instead of synthetic sound absorbing materials. This research investigated the sound absorption coefficients of coir fibres mat composed of a matrix and vertically placed core fibre layer with different thicknesses (20 mm and 25 mm). The coir fibre samples are tested in accordance with ISO 10534-2 standards within the frequency range from 63 to 6300 Hz. The PLACID Impedance Tubes with 100 mm and 30 mm diameters are used to observe the data within the whole frequency range. Absorption coefficient data observed for coir fibre mats are compared with the Polyurethane samples of the same thickness of 20 mm. The results depict that the coir fibre mat has good acoustic absorption performance in high frequency range compared to that of the polyurethane sample. The absorption coefficients of both coir fibre mat and the Polyurethane sample are very close at low frequencies. Additionally, two coir fiber mat samples with varying thicknesses were also tested. Approximately 33.33% of improvement in sound absorption is performed with the higher thickness coir fibre composite (25 mm) compared to the lower thickness (20 mm) sample. This study reveals that there is enormous potential to use the natural fibre composites as sound absorbing materials.