186 Lecture 10 
teristic V pattern of the hard bottom is evident in the deeper water. In the 
records shown in Figs. 10.22 and 10.23, the water is in both cases 2 in. deep and 
the bottom plate glass. In the first series (Fig. 10.22), the records cover the 
range of depth from midwater to surface, while in the second series they extend 
from bottom to midwater. It should be noted that in the first series the range 
extends from 0.05 to 4.5 m, andthe last record (transmitter near the surface) 
shows Lloyd's fringes very clearly at the short ranges. In the shallower water 
record (1 in. deep) shown in Fig. 10.24, the pattern is still complex but shows 
signs of more regularity than that in the deeper (2 in.) water. 
It is interesting to notethe changes inthe pattern when small depth changes 
are made. This is shown in Fig. 10.25, where records have been made in water 
of depth 50 mm reduced by steps of Wp mm. If a particular feature of the records 
is selected, for example the inverted V near the 3.5-m mark on the records, it 
will be observed that this moves slightly to the left with each '/,-mm decrease 
of depth. Similar drifts to the left are noticeable on other outstanding features, 
the drift decreasing with decrease of range from the transmitter. A comparable 
effect is seen in Fig. 10.26, where the wavelength (frequency) is varied in 
steps. Such records emphasize the relationship which must exist between depth 
and wavelength in delineation of the sound field. 
0.6M (1) 450 KC 4.3M 
Fig. 10.26. Picture show- 
ing the effect of small fre- 
quency variations. Water 
2.0 in. deep, the bottom is 
(2) A425 KC rubber-covered, and the 
frequency is 560 kcps. 
(3) 400 KC 
(4) 450 KC 
