Multiplying resonances for attenuation in mechanical metamaterials: Part 1 – Concepts, initial validation and single layer structures

•Three different locally resonant structure families were studied: spherically symmetric, flexural single-resonance and flexural multi-resonance.•Some resonator elements showed a peak effective mass much greater than their rest mass and achieved peak transmission losses 10’s of dB greater than a non-resonant structure of equivalent surface density within the designated frequency range.•A large (2.5 m2) test article was constructed and tested under full-scale diffuse field conditions such as are found in buildings.•The results confirmed that the bandgap observed in impedance tube measurements of small-scale LRS specimens survives.