Determination of the acoustical properties of sisal and coconut fiber samples based on the flow resistivity experimental assessment

• Published in: The Journal of the Acoustical Society of America 2016-10, Vol.140 (4), p.3141-3141
• Main Authors: Lima, Key F., Barbieri, Nilson, Barbieri, Renato, Grossl, Vinicius A.
• Format: Article
• Language: English
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.4969846

Absorbent materials are fibrous or porous and must have the property of being good acoustic dissipaters. The noise reduction process occurs due to transformation of a part of the sound energy into heat. The attenuation is caused by friction of the viscous air fluid inside the irregular arrangement of fibers during the sound wave propagation. This study assesses the complex wave number and the complex characteristic impedance of two natural fibers with the classical empirical equations of Delany and Bazley (1970). These properties are determined based on experimental evaluation of the flow resistivity of sisal and coconut coir fiber samples. The experimental assessment procedure was performed according to the guidelines of ASTM C522-03 (2009). Samples evaluated have approximately identical densities, different diameters, and thicknesses. The diameters were 62.0, 71.5, and 80.0 mm and thicknesses were 5, 10, 15, and 20 mm. The purpose of testing seven dimensions is to verify the effect of these differences on the flow resistivity experimental measurements. This evaluation is due the standard ASTM does not provide guidelines for the sample dimensions.