Approaching a methodology for the development of a multilayer sound absorbing device recycling coal bottom ash

Abstract

The aim of the present work has been to develop a methodology which accurately predicts the acoustic behavior of a material without having to manufacture large panels and testing them in reverberation room. Moreover, it can be predicted the sound absorbing performance at normal and random incidence of the sound wave on a material for different thicknesses and multilayer configurations, dramatically reducing the number of experimental tests. This methodology might decrease the cost of the investigation, which is particularly important when dealing with recycled materials that must compete with commercial products used in the same application.The designed methodology consists of determining the acoustic intrinsic properties (open porosity, tortuosity and static airflow resistivity) of bottom ash-based concretes with different particle sizes by an indirect method. This method uses the acoustic absorption coefficient measurements obtained in the impedance tube and the mathematical equations that describe the acoustic behavior of porous materials, implemented in the software CARAM. With the intrinsic properties, the thickness of the panel and the vibroacoustic behavior simulation software SIMAM, simulations of the sound absorption coefficient are performed and compared to the experimental results at normal incidence in the impedance tube and at diffuse incidence of a multilayer panel tested in reverberation room.From the results obtained it can be concluded that the methodology proposed in this work gives accurate results of the acoustic absorption of products at industrial scale, with the advantages of requiring small specimens of the materials to carry out the characterization tests, and decreasing the total cost of the investigation.