Acoustic metamaterial antennas for combined highly directive-sensitive detection

Detection of weak sound signals masked by strong noise background remains challenging in acoustic science and engineering. The major bottleneck of advancing this technology is the limited directivity and sensitivity of ordinary acoustic sensors. Here, we engineer acoustic metamaterials with a near-zero-index (NZI) in the form of a low-profile planarized acoustic antenna for combined highly directive-sensitive detection. The detectable incident angle can be substantially narrowed down by the directional selectivity of NZI acoustic metamaterials, while the detected pressure can be enhanced by deeply tunneling compression at the sound radiation vent. Magnification of signal amplitude more than 18 dB with a half-power beam width of mainlobe less than 5° is demonstrated both numerically and experimentally, which overcomes the detection limit of conventional acoustic sensing systems.