Hypersonic spectroscopy for materials characterization

Article By:

Snow, Paul A. Department of Physics, University of Bath, Bath, Somerset, United Kingdom.

Last reviewed:2014

DOI:https://doi.org/10.1036/1097-8542.YB140420

Hypersonic spectroscopy is the measurement of the relative interaction of different very high frequencies of sound with a solid elastic sample. The description “hypersonic” indicates that the frequencies are greater than 1 gigahertz (GHz, 10⁹ or one thousand million oscillations per second). The elastic properties of materials, quantitatively describing the deformation of the material caused by applied forces, are measured by this technique, and the high frequencies, corresponding to a short wavelength for the sound, make the technique ideal for investigating materials with very small features of the order of micrometers (1 μm = 10⁻⁶ m, one millionth of a meter). The internal movements of the material caused by the wave can be in the direction of energy propagation of the wave (a longitudinal wave, such as sound) or perpendicular to it (a transverse wave), so that the waves, as they go through the material, are more correctly described as elastic waves rather than sound waves.

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