Sukhovich, Alexey Department of Physics and Astronomy, University of Manitoba, Manitoba, Winnipeg, Canada.
Page, John H. Department of Physics and Astronomy, University of Manitoba, Manitoba, Winnipeg, Canada.
- Band gaps
- Negative refraction and sound focusing
- Links to Primary Literature
- Additional Readings
Phononic crystals are periodic composite materials made from constituents with different densities and acoustic wave velocities. These synthetic materials, which are analogous to photonic crystals for electromagnetic waves, are of growing interest because they can change the way in which sound or ultrasound travels through matter, leading to a number of novel applications. Phononic crystals may be constructed by arranging identical objects [for example, rods in two dimensions (2D) or spheres in three dimensions (3D)] in a regular periodic array or crystal lattice, and embedding these elementary units in a host material or matrix. The key feature of phononic crystals is their periodicity, which causes the propagation of acoustic or elastic waves to be dramatically modified when length scale of the periodicity is comparable with the wavelength of sound (or ultrasound). The origin of these effects is the interference of waves scattered from the periodically arranged constituents. The overall size of phononic crystals may vary from several meters down to several micrometers, depending on the size of the elementary units (such as the diameter of a sphere or a rod), the lattice constants (the shortest distances over which the structure repeats), and the number of layers. The condition that these characteristic lengths be comparable to the wavelength dictates the operational frequency range of the phononic crystal, which can thus be tuned from hundreds of hertz to gigahertz.
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