E. Meyer 147 
o/ 
600b aya” i 
em“‘sec? sx 3 
+5 
400 
Fig. 9.9. Attenuation in water asa 
function of the ratio of sound pres- 
sure and frequency. 
200 
we P/vatinos: Mc7! 
7 (Stns re: 
0 10 20 J0 
1) 365 Mc, 2) 585 Mc, 3) 68 Mc, 
4) 874 Mc; 5) 15 Me, 
pecially, E. Hiedemann and his co-workersin East Lansing and I. G. Mikhailov 
and V.A. Shutilov in Moscow have studied these problems. Figure 9.10 displays 
diffraction spectra obtained at 1.76 Mcps taken from a recent publication by 
E. A. Hiedemann and M. A. Breazeale [13]. The spectra are arranged horizontally 
according to the distance between test point and sound source and vertically 
according to increasing sound intensity given by the Raman—Nath parameter 
V =27p-L/X, where L is the depth of the sound field, A is the wavelength, and yu is 
the amplitude of fluctuation of the index of refraction. V =7,5 corresponds approxi- 
mately to a pressure amplitude of 1 atm in the vicinity of the sound source. 
The dissymmetry is acharacteristic feature of the spectra which are symmetrical 
at low intensities; this dissymmetry increases with increasing intensity and in- 
creasing distance from the sound source. The explanation of this effect is rather 
simple. At high intensities and large distances, the sinusoidal sound wave in the 
liquid is increasingly distorted to form a saw-toothed curve. Consequently, the 
36 ony 
Sound warns 
; 0 
Ss Bae ae pees Pe 
| 
a ‘ , 
Fig. 9.10. Light diffraction by ultrasonic waves in water at 1.76 Mc. 
