Acoustic metamaterial in low-frequency underwater noise mitigation

With the rapid expansion of offshore facility deployments, there is growing interest in developing effective underwater noise mitigation measures to protect marine ecosystems. Conventional strategies such as hydro-dampers, bubble curtains, and metal casting layers are limited in their ability to suppress broadband low-frequency noise while offering portability and cost-efficiency. Over the past decades, metamaterials have demonstrated remarkable versatility for noise control. In this work, we propose a lightweight, easily manufactured metamaterial design that can specifically mitigate wide-band low-frequency underwater noise through the sound-insulation mechanism. Lab-scale tests using the 3-D-printed structure have shown its capability of noise attenuation of approximately 25 dB across more than three octaves, with a maximum reduction level of about 60 dB.