Ordinary sound-blocking materials rely on mass — thick, heavy walls attenuate low frequencies poorly. A locally resonant acoustic metamaterial instead embeds a lattice of small sub-wavelength resonators (a heavy mass on a soft spring) inside a lighter host structure. Near each resonator's own natural frequency, it swings out of phase with the driving wave and effectively acts as a negative dynamic mass, reflecting the incident sound back rather than letting it pass. This carves a bandgap — a frequency window in which transmission collapses — that can sit far below the wavelength the slab's physical thickness would normally allow.
Because the bandgap frequency depends on the resonator's own mechanics rather than the lattice spacing, acoustic metamaterials can block wavelengths dozens of times longer than the material itself — something impossible for conventional mass-law soundproofing at any practical thickness.
A 3D lattice of engineered sub-wavelength resonators embedded in a host structure, where each unit cell's own resonance can absorb and reflect a chosen band of sound frequencies before they reach the far side.
Locally resonant metamaterials create a bandgap set by resonator mass and coupling stiffness, not by lattice thickness — inside that band, wave amplitude decays exponentially cell to cell instead of propagating.
Sweep the drive frequency through the lattice, then retune the resonator mass and coupling stiffness to move and widen the purple bandgap on the strip chart, watching the 3D wave die out or pass through in real time.
Because resonance — not slab thickness — sets the blocked frequency, acoustic metamaterials can attenuate wavelengths many times longer than the material itself, beating the classic mass-law limit of conventional soundproofing.