A pulsed phase-sensitive technique for acoustical measurements

Abstract

The pulsed phase-sensitive (PPS) technique for measurements of sound velocity and attenuation in fluids and solids is reviewed. With this technique, which uses a cycle-overlap principle, a time delay is measured between any two acoustical pulses transmitted through a sample or reflected from its boundaries. A current realization of the technique allows one to resolve the time-delay variation down to 0.1 ns. Thus at relative measurements with the PPS technique, precise sound velocity data can be obtained for samples of small thickness (about 1 mm). The technique is versatile and can also be used for accurate absolute measurements. The technique is most advantageous for studies of samples with high attenuation, in particular near phase transitions and at high temperatures. The technique also allows one to measure sound attenuation with moderate accuracy. An application of the technique that employs narrow-band radio frequency (rf) bursts for relative measurements of the phase sound velocity is considered in detail. The technique is applied to studies of liquid alkali metals and mercury at temperatures up to 2100 K and pressures up to 200 MPa. As a verification of the capabilities of the technique, new results are presented on sound attenuation in mercury in the metal–nonmetal transition region. A table for sound velocity in mercury at temperatures from 550 to 1900 K and pressures up to 190 MPa is presented in the Appendix.