Novel negative mass density resonant metamaterial unit cell

•A novel acoustic metamaterial unit cell provides Lorentz-type resonant effective mass density.•Analytical formula for effective mass density is derived.•Acoustic bandstop medium and left-handed metamaterial based on the novel unit cell are presented.•Modified version of the unit cell, operating at two independent frequencies, is proposed.

In this paper a novel resonant unit cell of one-dimensional acoustic metamaterials is presented, which exhibits negative effective mass density. We theoretically analyze the unit cell and develop a closed analytical formula for its effective mass density. Then we proceed to demonstrate left-handed propagation of acoustic waves using the proposed unit cell. Finally, we present its dual-band version, capable of operating at two independent frequencies.