| Popis: |
The surface velocity response to acoustic excitation of sand contained within a thick‐walled PVC tank in the shape of a truncated cone has been investigated with and without buried objects. The excitation was provided by either tonal or white‐noise spectra from a large loudspeaker, and the sound field was localized above the buried objects by means of an inverted cone and pipe arrangement. The surface velocity of the sand has been measured with an accelerometer. The loading effects of the accelerometer have been found to be minor. The surface admittance spectra above a buried plastic container are found to have uniquely resonant structures, the nature of which has been investigated. It has been found that if the surface of a granular medium, containing buried objects, is subject to high levels of sound using either a single frequency or two separate frequencies, then, as well as an enhanced linear surface velocity response at the excitation frequencies, increased quadratic and cubic nonlinear responses ma... |
