Broadband Low-Frequency Acoustic Metamuffler

In this research, we propose and design an acoustic metamuffler (AMM) by coupling a microperforated plate composite waveguide formed main Helmholtz resonator. The proposed mechanism deliberately designed structure are conducive to generating multimode resonances that help improve the absorption effect lead broadband (4 octaves) sound insulation. We develop effective circuit model analytically predict insulation bandwidth put forward numerical experimental measurements demonstrate effectiveness of concept. AMM produces with average 20 dB sound-transmission loss at low-frequency range, extending from 100 1600 Hz, while having ultrathin thickness 6.2 cm (1/55\ensuremath{\lambda} for lowest working frequency). Our findings could have pragmatic applications insulators or absorbers.