Ultra-broadband sound absorption performance of a multi-cavity composite structure filled with polyurethane

In order to improve the sound absorption performance of the resonator, porous materials are introduced, an acoustic metamaterial structure (P_TMCCR) composed of a tunable multi-cavity coupled resonator (TMCCR) and polyurethane-filled slits was established. Firstly, the TMCCR was designed by combining theoretical research with finite element simulation, which enables the continuous ultra-broadband sound absorption performance by adjusting the resonant frequencies of each component. Secondly, a simulation model of the P_TMCCR was established and its effectiveness verified through an impedance-tube test. Finally, sound absorption effects of polyurethane infill and the influences of various filling modes were investigated. The results demonstrate that the P_TMCCR (after filling) exhibited a significantly improved sound absorption bandwidth and coefficient, leading to more stable sound absorption effects. The double-layer P_TMCCR effectively absorbs sound within 375 to 4270 Hz and the average sound absorption coefficient exceeded 85% from 430 to 2370 Hz, filling the bottom with polyurethane and communicating with the incident surface can significantly improve sound absorption in the frequency band less than 250 Hz. The P_TMCCR is easy to prepare and its frequency band of sound absorption is adjustable on demand to realize continuous and stable sound absorption effects, suggesting potential for use in sound absorption and noise reduction applications.