Numerical and experimental investigation of membrane-type acoustic metamaterials for sound-insulating enclosure design

Membrane-type acoustic metamaterials represent a promising class of lightweight structures capable of achieving significant low-frequency sound attenuation through localized resonance phenomena. Unlike conventional noise-control materials governed by the mass law, they enable substantial transmission-loss enhancement without a notable increase in mass, making them attractive for applications, where weight constraints are critical. This contribution presents a numerical model describing the vibroacoustic behaviour of membrane-type resonant structures and examines design strategies for tailoring their acoustic performance. Additionally, the potential of combining such metamaterials with traditional insulating materials was evaluated to enhance the low-frequency attenuation of noise-control enclosures. The numerical predictions were validated through experimental measurements of the sound reduction carried out under reverberant conditions for a prototype enclosure wall composed of a conventional insulating material supplemented with membrane-type metamaterial modules. Comparison of the measured data with the numerical results enabled an assessment of the model’s accuracy and confirmed its ability to reproduce the overall acoustic behaviour of the hybrid system. The findings demonstrate the effectiveness of membrane-based metamaterials in targeted low-frequency noise reduction and highlight their potential for application in lightweight sound-insulatingstructures.