This paper reports the results of measurements of the attenuation and velocity of ultrasonic waves in various liquid media as a function of the intensity level at the detector of the radiation. The attenuation in distilled water and dilute solutions of acetic acid and sodium acetate is found to increase almost linearly with the acoustic excess pressure amplitude in the range from 2 to 7 atmospheres, for frequencies of 4, 5, 7, and 9 megacycles/sec. The attenuation in glycerine shows a similar increase when correction is made for the unavoidable rise in temperature of the medium. The rate of increase is found to be practically independent of frequency in the range employed, thus disagreeing with the prediction of R. D. Fay's theory of the attenuation of high-amplitude plane waves. No change of velocity with source intensity has been observed.
In this second article on the Filtration of Sound, Professor Lindsay describes particularly filtration in solid media. It contains also a survey of recent developments.
Calculation is made of the transmission of harmonic compressional waves through a finite solid filter structure consisting of a metal rod loaded at equal intervals with heavy metal collars. The theory is then tested experimentally for the special case where the finite structure (consisting of 6 sections) is terminated by a finite rod with a free end. The structure acts as a low pass filter with a cut-off at about 2000 cycles and no further transmission up to 12,650 cycles. The transmission in the transmission band shows a series of peaks whose positions, with one exception, are accurately verified experimentally. 42 R. B. LINDSAY AND A. B. FOCKE
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