The acoustic nonlinearity parameter B/A is determined using a method based on the finite amplitude distortion of a sine wave emitted by a piston. The growth of the second harmonic component of this wave is measured by a piston receiver which is coaxial with and the same size as the source. In order to determine B/A, the experimental measurements are compared to a theory which incorporates the nonlinearity parameter. The theory developed for this study accounts for the influence of both diffraction and attenuation on the experimental measurements. For this reason, the method is more accurate than previous techniques that employ plane-wave theory for a lossless medium. To test the measurement method, experimental results for B/A in distilled water, ethylene glycol, and glycerol are compared to established values. The agreement between these values suggests that the measurement accuracy is ±4% for common liquids.

A technique for measurement of the acoustic nonlinearity parameter B/A in liquids is presented, along with results for several liquids. The nonlinearity parameter is determined by measuring changes in the travel time of ultrasonic tone bursts which are caused by prescribed changes in the ambient pressure. The travel time differences are measured by comparing the phase of the tone burst with that of a reference signal. The measurement is simpler to perform than those previously reported in the literature.

Our results point to the potential use of USHT as a reversible and noninvasive approach to increase BBB permeation of hydrophobic drugs, including P-gp-recognized substrates.

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The acoustic nonlinearity parameter B/A is determined using a method based on the finite amplitude distortion of a sine wave emitted by a piston. We measure the growth of the second harmonic component of this wave using a piston receiver, which is coaxial with and the same size as the source. In order to determine B/A, the experimental measurements are compared to a theory which incorporates the nonlinearity parameter. The theory developed for this study accounts for the influence of both diffraction and attenuation on the experimental measurements. For this reason, the method is more accurate than previous techniques that employ plane wave theory for a lossless medium. To test the measurement method, we compare the experimental results for B/A in distilled water, ethylene glycol and glycerol to established values. The agreement between these values suggests that the measurement accuracy is plus or minus 4% for common liquids. [Work supported by ONR.]