48 Lecture 2 
MEAN VALUE 
@) 
$500 
.¢ 
4 250 
Ww 
& DISPLACEMENT 
OQ 20 40 60 80100 120 140'160 180 200 220 240MM 
1O» 20x 30x 40x 50x 60x 7OXx 80> 
MV 
1000 
750 
a 
» MEAN VALUE 
= AGO) HORIZONTAL 
r L LACE MENT 
O 20 40 60 80'1I00 120 140'I60 180 200 220240MM 
1OAX 20x 30A 40x 50>» 60x 7OX% 80> 
MV 
500 
400 
a 
> 
< 300 
(©) & 
200 
100 HORIZONTAL 
MOTION 
DISPLACEMENT 
Oo 20 40 60 80 I100 120 140' 160 180 200 220240MM 
lOxX 20X 302A 40» 50X 60X 7OX 8OX 
Fig. 2.18. Amplitude fluctuations due to lateral motion of the transducers in tank test at 500 kcps. 
Pulse duration 0.1 msec. Amplitudes recorded at fixed time-point in returned pulse. (a) Tank 
bottom covered with plaster of paris. grain size </12, undulations less than 0.5 in. high. (b) 
Tank bottom covered with sand, grain sizeA/12toA /3, undulations less than 0,5 in. high, (c) Tank 
bottom covered with sand and gravel, grain size A /12 to 3A, undulations less than 0,5 in, high. 
Abscissa shows lateral displacement of transducer in a plane parallel to mean level of bottom. 
2.6. CONCLUSIONS AND ACKNOWLEDGMENTS 
It is hoped that this paper has shown some ways in which useful progress 
may be achieved in the development of sonar systems. The work and ideas de- 
scribed owe much to the author's colleagues mentioned in the text, and to others 
(especially research students) too numerous to mention. The cooperation of the 
National Institute of Oceanography in providing ship facilities (including a trans- 
