A low-frequency sound insulation metastructure with relatively high ventilation

Abstract

Noise pollution is growing nowadays and there is always a conflict between ventilation and noise insulation. The advances in acoustic metamaterials provide an effective solution for this conflict. In this paper, we propose a metastructure with protruded necks based on Helmholtz resonance. Sound transmission loss (STL) of 13 dB at low-frequency of 488[Formula: see text]Hz is obtained in experiment with the ventilation of 20%, which is in good agreement with the simulation. It is revealed that introduction of protruded neck can reduce the resonant frequency. Sound absorption is the main mechanism for noise insulation at low frequency. Next, the effects of geometric parameters on sound insulation are discussed. A reduction in cross-sectional area of neck, an increase in neck length, and an increase in ventilation all lead to a decrease in both resonant frequencies and STL amplitudes. Finally, a two-layer structure is constructed by the proposed metastructure with different neck length in each unit. Both the amplitude and frequency range of STL are enlarged. These results exhibit a practical application for ventilated metastructure in sound insulation at low frequency.