A monostable acoustic metamaterial for broadband low frequency sound absorption
* Presenting author
This paper presents a monostable membrane-type acoustic metamaterial (MAM) for achieving a broadband sound absorption in low frequencies. The proposed monostable MAM is realized by placing a prototypic MAM with a magnetic proof mass in a symmetric magnetic field. An equivalent circuit model of such a system is presented. It is shown that the monostable MAM exhibits rich nonlinear dynamic features. The sound absorption peak significantly shifts downwards with the increasing magnetic field. Frequency sweeping test clearly shows the softening hysteresis phenomenon. To quantify the sound absorption performance of the nonlinear system, an energy index is proposed and indirectly obtained from the velocity of the proof mass measured by a laser vibrometer. Experiments demonstrate that the proposed design can realize a broader sound absorption bandwidth than its linear counterparts in the low frequency range.