Author(s): Liao Yunhong, Cheng Yong, Zhao Yuchen , Zhou Xiaoming
Noise attenuation is highly desirable in lots of engineering fields, yet it is hardly attained in the low-frequency regime. Developed rapidly in the past decade, acoustic metamaterials are providing a new route for low-frequency noise suppression in the form of compact and lightweight structures. The existing challenge is to break the narrow-bandwidth constraint due to the inherent local resonance. In this work, we propose to broaden the frequency bandwidth by using adaptive metamaterials. The studied adaptive metamaterial consists of a flexible plate with piezoelectric shunting. An analytical acoustic model is established, combining the dynamic coupling among piezoelectric shunting, plate structure, and acoustics, for the accurate estimation of sound transmission loss (STL) and sound absorption. Theoretical analyses show that piezoelectric structures with the shunting circuit may act as a spring element with frequency-dependent stiffness. This provides us an additional degree of freedom to trace the high STL or high absorption trajectory in the broad frequency range. The designed adaptive metamaterial can achieve over 40dB STL in the super broadband frequency from 10 Hz to 1 kHz. Supposed that the same target STL ~25dB is needed in the band ~180-2000Hz, the adaptive metamaterial can be 30 times lighter than passive metamaterials without containing active elements. In the different design of adaptive metamaterials, the near-unity sound absorption can be achieved in the broad band starting from very low frequencies. The full-wave simulation has also been conducted, showing very good agreement with analytical results. Our study provides a promising mechanism for the broadband noise attenuation with extreme lightweight structures.
Name: Prof Xiaoming Zhou