In the quest to mitigate urban noise pollution, researchers have turned their attention to the humble road surface, and a recent study published in *Case Studies in Construction Materials* (translated from Chinese as *Case Studies in Building Materials*) is making waves in the construction and energy sectors. The research, led by Gongyun Liao from Southeast University in Nanjing, China, delves into the sound-absorption capabilities of double-layer porous asphalt (DLPA), offering insights that could revolutionize pavement design and urban planning.
Traditionally, the sound-absorption performance of DLPA has been evaluated using macroscopic approaches, which consider the material’s overall properties. However, Liao and his team took a different tack, conducting a mesoscopic analysis through acoustic simulations. By reconstructing the three-dimensional (3D) mesoscopic pore structure of DLPA using an integrated approach—combining X-ray CT scanning, discrete element method (DEM), and digital image processing—they were able to examine the material’s acoustic behavior in unprecedented detail.
The team employed three macroscopic parameters and three mesoscopic parameters to characterize the DLPA’s properties. Using laboratory-validated finite element method (FEM) simulations, they assessed how these parameters individually and jointly affected the sound-absorption performance of DLPA. The results were striking. “We found that the lower-layer parameters exerted approximately twice the influence on sound absorption compared to the upper-layer characteristics,” Liao explained. This discovery could have significant implications for the design and construction of future road surfaces.
The study revealed that the maximum noise attenuation of 27% was achieved by elevating mesoscopic and macroscopic characteristics in the lower layer (except thickness) while reducing equivalent upper-layer parameters. Moreover, DLPA with “two-sieve-gap” configurations, such as PA-10 + PA-20, demonstrated superior sound absorption performance compared to conventional “one-sieve-gap” designs like PA-13 + PA-20. This is due to Helmholtz resonance effects, which enhance the material’s ability to absorb sound waves.
The commercial impacts of this research are substantial. By optimizing all three mesoscopic parameters, noise-reduction coefficients of 0.4 can be achieved, providing a scientific basis for designing high-performance DLPA pavements with exceptional acoustic properties. This could lead to quieter urban environments, improved quality of life for residents, and reduced noise pollution-related health issues.
For the energy sector, the implications are equally significant. Quieter road surfaces can contribute to more efficient and sustainable urban planning, reducing the need for noise barriers and other mitigation measures. Additionally, the enhanced sound-absorption capabilities of DLPA could lead to more efficient energy use in urban areas, as less energy would be required to mask or mitigate noise pollution.
As cities around the world grapple with the challenges of urbanization and noise pollution, this research offers a promising solution. By targeting the mesoscopic pore structure of DLPA, engineers and urban planners can design road surfaces that not only withstand the rigors of daily use but also contribute to a quieter, more sustainable urban environment. The study by Liao and his team is a significant step forward in this endeavor, providing a scientific foundation for the development of high-performance, sound-absorbing pavements.
In the words of Liao, “This research provides a scientific basis for designing high-performance DLPA pavements with exceptional acoustic properties.” As the construction and energy sectors continue to evolve, the insights gained from this study could shape the future of urban infrastructure, paving the way for quieter, more sustainable cities.