A pulsed phase-sensitive technique for acoustical measurements

The pulsed phase-sensitive (PPS) technique for measurements of sound veloci ty and attenuation in fluids and solids is reviewed. With this technique, w hich uses a cycle-overlap principle, a time delay is measured between any t wo acoustical pulses transmitted through a sample or reflected from its bou ndaries. A current realization of the technique allows one to resolve the t ime-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 s mall thickness (about 1 mm), The technique is versatile and can also be use d for accurate absolute measurements. The technique is most advantageous fo r studies of samples with high attenuation, in particular near phase transi tions and at high temperatures. The technique also allows one to measure so und attenuation with moderate accuracy. An application of the technique tha t employs narrow-band radio frequency (rf) bursts for relative measurements of the phase sound velocity is considered in detail. The technique is appl ied to studies of liquid alkali metals and mercury at temperatures up to 21 00 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 mercur y at temperatures from 550 to 1900 K and pressures up to 190 MPa is present ed in the appendix. (C) 1999 Acoustical Society of America. [S0001-4966(99) 06412-7].