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Copyright of Lettre de Medecine Physique et de Readaptation is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Pelvi-Perineologie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A description is given of a technique for measuring small ultrasound velocity differences between two liquids, based on a new high resolution phase comparison method. The technique uses a two-path acoustic system well suited for velocity dispersion measurements in the frequency range 3.3 to 330 MHz. The phase difference between two acoustic pulses traveling through the liquid is measured with a resolution of a few picoseconds. Velocity differences can be measured with an accuracy of ±1.5 cm/s. The unusually wide frequency capability and accuracy of the method are demonstrated with dispersion measurements on polystyrene samples dissolved in ethylbenzene. [ABSTRACT FROM AUTHOR]

An improved differential phase-comparison method for the measurement of small changes in ultrasonic velocity is described. Velocity dispersion measurements can be carried out in the frequency range from 3.3 to 70.2 MHz; the relative accuracy is one part in 105; only 12 cm3 of liquid are required. Results are presented for aqueous and organic solutions, which are in good agreement with known ultrasonic-absorption data. Subject Classification: 35.24, 35.35. [ABSTRACT FROM AUTHOR]