Broadband and Intense Sound Transmission Loss by a Coupled-Resonance Acoustic Metamaterial

The advent of acoustic metamaterials has opened up an emerging frontier in the control of sound transmission. A key limitation, however, is that an acoustic metamaterial based on a single local resonator in the unit cell produces a restricted narrow-band attenuation peak. When multiple local resonators are used, the attenuation peaks that arise-while numerous-are each still narrow and separated by passbands. Here, we present an acoustic metamaterial concept that yields a subwavelength sound transmission loss through two antiresonances-in a single band gap-that are fully coupled and, hence, provide a broadband attenuation range; this is in addition to delivering a high isolation intensity for both peaks that exceeds 100 dB within the 3-5 kHz range or 60 dB around 1 kHz. The underlying coupled-resonance mechanism is triggered by ensuring that two local resonances appear between two coincident frequencies formed by the intersection of the incident acoustic waves sound line with Bragg dispersion curves governing in-plane wave motion orthogonal to the direction of transmission. This phenomenon is nominally realized in the form of a thin single-panel single-material pillared-plate structure with internal contiguous holes, a practical configuration that lends itself to design adjustments and optimization for a frequency range of interest, down to subkilohertz, and to mass fabrication.