Elastic/Acoustic metamaterials provide an approach through which the effective homogeneous bulk parameters (density and modulus) of a system composed of an often periodic sub-structure can take extreme and negative values across finite frequency bands. Previous research suggests that they provide a suitable approach to lightweight sound and vibration control. With the integration of sensors and actuators into the metamaterial sub-structure its motion can be actively controlled using digital feedback loops. This control can be used to create a response that would not be possible with passive components alone, or can be used to tune the effective parameters on demand. This paper presents the results of a study on active elastic metamaterials with tuneable negative effective density and modulus bands. An important implication of the work is that it potentially allows a standard design to be applied to different applications or to adapt to environmental or user demands.
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