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58
14. CHARACTERISTICS OF THE
ULTRASONIC WAVE IN WATER
The purpose of this chapter is to provide an overview of the charac-
teristics of the ultrasonic wave in water.
Sound Velocity
It is generally known that an ultrasonic wave travels 1500 meters per
second in sea water, but in practice, some amount of variation arises
depending on the season and area from differences in the following
three factors:
Water temperature ..............................θ [ C]
Salinity density ................................... S [%]
Water pressure (water depth).............. h [m]
Therefore, for propagation in surface water the velocity changes not
only by area but also by direction of the wave propagation. The equa-
tion obtained thru numerous measurements is;
C= 1410 + 4.21θ - 0.037θ
2
+ 1.145S + 0.0168h [m/s]
°C
°C
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
1445.4
1450.0
1454.4
1458.8
1463.1
1467.2
1471.3
1475.3
1479.2
1483.0
1486.7
1490.3
1493.8
1497.3
1500.6
1503.8
1507.0
1510.0
1513.0
1515.9
1518.7
Velocity (m/sec)
Depth
(m)
5
10
15
20
25
1.8 3.6 5.4 7.3 9.1 10.9 14.5
1.8 3.6 5.4 7.2 9.0 10.8 14.5
1.8 3.6 5.4 7.2 9.0 10.8 14.4
1.8 3.6 5.4 7.2 9.0 10.8 14.4
1.8 3.6 5.4 7.3 9.1 10.9 14.5
100 200 300 400 500 600 700
Correction value with respect to
Depth and Temperature (m/s.)
Fig.1 Sound Velocity