Use of time delay spectrometry in fluid attenuation measurement

In the context of diagnostic ultrasound coupling fluid a technique is presented to measure fluid attenuation over a wide frequency range using time-delay spectrometry (TDS). With the TDS technique, a swept sinusoidal signal drives a wideband transmitter facing a wideband receiver at a known separation distance. By accounting for the time delay between the transmitter and receiver, it is possible to isolate the direct acoustic path from any reflected paths, through narrowband filtering. The attenuation measurement was conducted as a comparison of a water-only path and one with a sample of liquid interposed between the transmitter and receiver. Specially designed test cells were constructed to contain various liquids as thin planar slabs. The results of tests on several liquids, such as castor oil and polyethylene glycol, are given, and the advantages and limitations of the technique are pointed out. A significant advantage of the TDS-based approach is that it provides data as a virtually continuous function of frequency