DRS. GUY BARLOW AND H. B. KEENE ON THE ANALYSIS OF SOUND. 
157 
distance also involves a change in direction with respect to the vertical, and if nodal 
planes exist in the water one would expect a more complex relation than that given 
by the former experiments using non-directional sounders. There is the additional com¬ 
plication due to reflection from top and bottom, which will be different in the two sets of 
experiments owing to the sounder always being placed below, instead of on, the surface. 
Putting, as formerly (p. 153), amplitude qc ———^-— . the values of the index p for 
(CtlStflllCG j 
the different harmonics are given in the following table :— 
Depth of 
water.* 
Frequency, 
n. 
Responses at horizontal distance. 
Index p. 
ft. 
13 
11-1 
(14 ft.) 
(24 ft.) 
n 
90 
25 
2-4 
2 n 
210 
100 
1 -4 
on 
130 
37 
2-3 
4 n 
230 
60 
2-5 
5 n 
40 
7 
3-2 
16 
11-2 
(134 ft.) 
(21 ft.) 
(43 ft.) (69 ft.) 
n 
80 
25 
5 
0 
2-4+ 
2 n 
45 
25 
10 
0 
1 *3f 
3 n 
45 
10 
10 
5 
4 n 
140 
70 
23 
10 
1-6| 
26 
11-2 
(21 ft.) 
(42 ft. 
Boat 
rirplinty 
n 
28 
15 
0-91 (1-1)4 
2 n 
14 
5 
1-5 (1-6)4 
3 n 
25 
3 
3-1 (4-9)4 
The distances given in the table are 
horizontal distances, and these differ from 
the true distances more in deep than in 
shallow water. This correction has not 
been made, as it does not appear to lead to 
a simnler law. 
In fig. 13 the values of the log (amplitude) 
are plotted against log (distance) for the 
third experiment in the table, in which the 
greatest range of distance was covered. 
It will be seen that the graphs for n, 2 n and 
4 n are practically straight lines giving a 
constant value for p as determined by the 
slope of the line in each case. The results 
20 
/■o 
4-n. 
Lop dLstcuuze^ 
1-0 
Fig. 13. 
/■x 
j-i- 
/■6 
r-8 
20 
Variation of amplitude with distance- 
index graph. 
* The receiver was 6 feet above the bottom, 
f From graph, fig. 13. 
\ These values of p are calculated for the oblique distances. 
z 2 
