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 - 0.037θ2 + 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