The transit time of sound in a phononic crystal

Electron material waves cannot permeate a periodic atomic lattice at each energy or frequency. There exists a forbidden gap due to the periodicity of the atoms. In analogy, acoustic waves cannot penetrate a phononic or sonic crystal at each frequency. A two-dimensional sonic crystal consists of a periodic lattice of cylinders. The periodicity is adjusted according to the wavelength of sound. Depending on the frequency, there exist allowed bands with a propagation of the waves as well as a forbidden band without propagation corresponding to the bandgap in a semiconductor. The mathematical description of the phenomena in the sonic crystal and in the atomic crystal is technically similar. Here, we investigate experimentally the velocity of sound in a sonic crystal by measurement of the wave's transit time through the crystal. The velocity in the crystal depends on the frequency and is smaller than the velocity in air. (C) 2022 Author(s).

Automated summary

Electron material waves and acoustic waves are unable to penetrate periodic structures, resulting in forbidden bands. The velocity of sound in a sonic crystal depends on frequency and is slower than in air.