Polyurethane–natural fiber hybrid for high-performance acoustic panels

An unedited research paper published online in Scientific Reports reports the development of a high-performance acoustic absorber combining natural-fiber micro-perforated panels (MPPs) with an optimized polyurethane–fibrogranule (PU-FG) composite backing, offering a potential low-weight, renewable alternative for noise-control applications.

The manuscript, titled "Acoustic performance optimization of natural-fiber micro-perforated panels backed by an optimized polyurethane–fibrogranule composite", is currently available as an early-access, unedited submission, meaning it has not yet undergone final editorial processing and may contain errors or changes prior to its final version.

The work was led by Mojtaba Nakhaeipour and colleagues from the Isfahan University of Medical Sciences and Isfahan University of Technology in Iran, with collaboration from Aalto University in Finland. It addresses growing concerns over noise pollution and the need for environmentally compatible acoustic materials.

The researchers combined an alkali-treated flax- and rice-husk-based micro-perforated panel with a backing layer made from polyurethane reinforced with natural fibrogranules, derived from the same renewable fillers. Using response surface methodology and a central composite design, they optimized panel porosity, backing thickness and air-gap geometry.

The optimized configuration—featuring a 1.61% porosity MPP, a 40 mm PU-FG backing, and front and rear air gaps—achieved a sound absorption average (SAA) of 0.82 and a noise reduction coefficient (NRC) of 0.85 across frequencies from 100 to 2500 Hz. The authors attribute the broadband performance to the combined effects of Helmholtz resonance in the micro-perforated panel and visco-thermal energy dissipation within the porous polyurethane composite
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Microscopic analysis confirmed a hierarchical pore structure in the PU-FG backing, enhancing airflow tortuosity and interfacial adhesion between fibers and the polyurethane matrix. By significantly increasing renewable content while maintaining high acoustic efficiency, the study suggests a scalable pathway for sustainable polyurethane-based sound-absorbing materials for use in buildings, transportation and urban infrastructure.

The authors note that findings should be interpreted in light of the manuscript’s unedited status until the final peer-reviewed version is released.

Photo by Jonathan Velasquez on Unsplash

Scientific Reports