Broadband and deep subwavelength acoustic antenna based on Fabry-Perot-like acoustic grating resonators.

• Graded reflection acoustic grating metamaterial(GRAGM) broaden the working bandwidth. • The GRAGM enables to realize a deep subwavelength acoustic sensing. • The strong directional response of the GRAGM is able to localize sound sources. • The GRAGM can be regarded as an acoustic antenna. Acoustic grating metamaterials (AGMs) with exotic enhancement property and remarkable directional response are promising candidates to advance the metamaterial-based acoustic sensing. In this paper, a graded reflection AGM (GRAGM) is proposed to broaden the working bandwidth and reduce the device volume. In contrast with conventional periodic AGM, GRAGM with graded slit width can be viewed as a series of combined Fabry-Perot-like (FP-like) resonators. As a result, the working band is broadened twice by combining multiple resonant bands. The added reflection plate is capable of reducing the working frequency of GRAGM by manipulating the reflection phase at the boundaries with the maximum variation over than 280 Hz, which enables the GRAGM to work in a deep subwavelength scale. Moreover, the strong directional response of the GRAGM is able to localize sound sources. These exotic properties promise a number of potential applications, such as sound source localization, condition monitoring, and remote whispering. [ABSTRACT FROM AUTHOR]