Using Helmholtz resonator arrays to improve dipole transmission efficiency in waveguide

It is well known that the radiation efficiency of an acoustic dipole is very low, increasing the radiation efficiency of an acoustic dipole is a difficult task, especially in an ordinary waveguide. In addition, current acoustic superlenses all utilize in-phase sources to do the super-resolution imaging, it is almost impossible to realize super-resolution imaging of an acoustic dipole. In this paper, after using the Helmholtz resonator arrays (HRAs) which are placed at the upper and lower surfaces of the waveguide, we observe a large dipole radiation efficiency at the certain frequency, which gives a method to observe an acoustic dipole in the far field and offers a novel model which is promising to realize the superlens with a source of an acoustic dipole. We discuss how the arrangement of HRAs affects the transmission of the acoustic dipole.