Locally resonant meta-composite for sound-proof of building envelops: Analytical model and experiment

In this study, a new type of locally resonant unit is designed, analyzed and tested. Its effectiveness to be used as a sound-proof building envelop material is evaluated. Each unit consists of a hard circular plate adhered on the soft membrane that fixed in a rigid frame. This new type of locally resonant unit can easily be installed into building envelope materials, such as extruded hollow concrete, hollow wooden board and other types of light weight partition panels, to enhance their sound proof property. An analytical model is developed to describe the ability of this composite material in low-frequency sound blocking. The model provides a direct explanation for the nature of the system and an accurate method to calculate the effective mass per unit area. It is shown that the effective mass per unit area can turn to negative at certain frequency ranges, which could lead to a complete sound attenuation. In order to measure the sound transmission gap position and verify the theoretical model, experimental works are carried out. The experimental results show good agreement with the theoretical predictions.