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THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1952 



oscilloscope. Echoes due to end to end reflections also appear, being 

 attenuated by normal acoustic losses until they are undetectable by the 

 time the next pulse is applied. 



With only air surrounding the rod, a phase reference and amplitude 

 reference are obtained for the first received wave (or subsequent echoes 

 if greater sensitivity is desired). The rod is then immersed a definite 

 length in the litiuid to be measured, as shown in Fig. 4, with, a resulting 

 phase retardation and amplitude reduction. These are measured by em- 

 ploying the experimental circuit shown by Fig. 5. In order to allow the 



Fig. 4 — Photograph of complete torsional wave measuring equipment. 



