Investigation of the Acoustic Properties of Panels Made from Pine Cones and Waste Pulp in Mid and High Frequencies

Abstract

Background: Concerns regarding the environmental impacts of absorbers made from synthetic materials have provided a valuable opportunity to expand research on the application of natural materials as sound absorbers. This study aims to evaluate the efficiency of sound absorbers made from eco-friendly, natural, and recycled materials (pine cones and waste paper pulp) in sound absorption. Methods: In the present experimental study, six acoustic panels were produced from pine cones and six panels from waste paper pulp, and tested. For this purpose, after preparing the materials and initial processing, polyvinyl alcohol glue was used as a binder, and the materials were molded in cylindrical shapes with a diameter of 3 cm, at a pressure of 2 bar, with varying thicknesses (1, 2, and 3 cm) and densities (300 and 350 kg/m³). After drying, their acoustic properties were evaluated using the two-microphone impedance tube method according to the ISO 10534-2 standard, within the frequency range of 1000 to 6300 Hz. Findings: The average sound absorption for the pine cone samples at a density of 300 kg/m³ and thicknesses of 1, 2, and 3 cm was 0.40, 0.59, and 0.70, respectively. For the samples with a density of 350 kg/m³, these values were 0.43, 0.67, and 0.64, respectively. Additionally, the average absorption for the waste paper pulp samples at a density of 300 kg/m³ and thicknesses of 1, 2, and 3 cm was 0.55, 0.65, and 0.58, respectively. These values for the samples with a density of 350 kg/m³ were 0.58, 0.46, and 0.65, respectively. Conclusion: The acoustic panels made from pine cones and recycled paper pulp can be considered as eco-friendly, natural alternatives to synthetic fiber panels, aimed at reducing noise pollution in mid to high frequency ranges. © 2026, Isfahan University of Medical Sciences(IUMS). All rights reserved.