Vibro-acoustic analysis of parallel barriers integrated with flexible panels

In urban communities, parallel barriers are commonly erected for controlling environmental noise such as traffic and construction noise. However, owing to the multiple reflections between the parallel barriers, their performance may be worse than that of a single barrier. To improve the performance of parallel barriers, a small piece of flush-mounted panel backed by a slender cavity in an otherwise rigid wall of barriers is proposed. With the excitation of the incident wave from a sound source inside the parallel barriers, the flexible panel vibrates, and sound is radiated out to undergo acoustic interference with the sound field bounded by the parallel barriers. Consequently, the sound energy in this space and diffraction at the barrier top edge are reduced over a broad band in the low-frequency regime. A theoretical model for tackling the vibro-acoustic coupling between the sound field of the open cavity and the vibrating panel is established to investigate the noise reduction mechanism in the shadow zone. With optimal structural properties of the panel, an additional averaged insertion loss of approximately 5 dB can be achieved at 80–1000 Hz. The theorical results, which are experimentally validated, pave the way for the potential applications of the flexible panel devices (FPDs) for improving the noise reduction of parallel barriers.