  We propose the design of an impedance matching acoustic bend in this article.
The bending structure is composed of sub-wavelength unit cells with perforated
plates and side pipes, whose mass density and bulk modulus can be tuned
simultaneously. So the refraction index and the impedance of the acoustic bend
can be modulated simultaneously to guarantee both the bending effect and the
high transmission. The simulation results of sound pressure field distribution
show that the bending effect of the impedance matching acoustic bend is very
good. Transmission spectra of the impedance matching acoustic bend and the
acoustic bend composed of perforated plates only are both calculated for
comparison. The results indicate that the impedance matching acoustic bend is
successful in improving the impedance ratio and increasing the transmission
obviously.
