Transmission line method for the measurement of the acoustic nonlinearity parameter in biological liquids at very high frequencies

Nonlinear wave propagation in a system consisting of a liquid specimen held between two SiO2 buffer rods is studied as a new method of determining the acoustic nonlinearity parameter of liquids at very high frequencies. Since the sign of the nonlinearity parameter of SiO2 is opposite that for liquids, the system can be viewed as a transmission line containing regions of both positive and negative nonlinearity. The nonlinear characterization curve is employed in which the second harmonic component output of the receiving transducer is plotted as a function of propagation distance in liquids between the two SiO2 buffer rods. The nonlinearity parameter is determined by measuring the dip position at which the transducer output becomes zero in the curve. Measurements are reported for water and aqueous solutions of dextrose and dextran in the fundamental frequency range 100-200 MHz. (C) 1997 Acoustical Society of America.