Effects of the features of a green sound-absorbing material on its acoustical properties

Abstract

This paper focuses on the airflow resistivity of a sound absorber. The airflow resistivity is used to predict sound absorption coefficients using mathematical models. As most green materials have unique characteristics, such as fiber curliness and non-circular cross-sections, the effect of these characteristics on acoustical properties needs to be studied. This work firstly discusses the development of an experimental set-up for measuring airflow resistivity and then develops an equation for estimating the airflow resistivity of a green material incorporating its unique characteristics. Samples of fibers with different curliness values are formed, and the effect of curliness on airflow resistivity is measured. The curliness of natural fibers is quantified by defining a unique factor, known as the curliness factor. The equation for airflow resistivity prediction is formed by the application of the Ergun equation and the experimental results obtained, which is then validated for fibers of different curliness. The sound absorption coefficients of the samples with different curliness values are measured. It is observed that an increase in curliness increases the airflow resistivity and sound absorption coefficient. The mathematical model proposed by Miki is used to predict the sound absorption coefficient, and the predicted results are compared with the measured results.