R2Sonic 2026 - Table 18: Absorption Values for Seawater and Freshwater at 400 Khz and 200 Khz

Page 178 of 254
Version
6.3
Rev
r012
Date
05-11-2022
Part No. 96000001
The below table and charts illustrate how frequency, water temperature, and salinity affect
absorption
Seawater Absorption Values: Salinity = 35ppt, pH=8
2
dB/km
400kHz
200kHz
Temp (C)
5°
10°
15°
20°
25°
5°
10°
15°
20°
25°
Depth (m)
50
97
100
111
130
154
46
56
68
80
89
100
96
100
110
128
153
46
55
67
79
88
150
96
99
110
128
152
46
55
66
78
88
200
95
99
109
127
151
45
55
66
78
87
250
95
98
109
126
150
45
54
66
77
86
300
95
98
108
125
149
45
54
65
77
86
400m
44
53
64
76
84
Mean Value
96
99
110
127
152
45
55
66
78
87
Freshwater Absorption Values: Salinity = 0.5ppt, pH=7
dB/km
400kHz
200kHz
Temp (C)
5°
10°
15°
20°
25°
5°
10°
15°
20°
25°
Depth (m)
50
65
55
46
39
33
17
14
12
10
9
100
65
54
46
38
33
17
14
12
10
9
150
65
54
45
38
33
17
14
12
10
9
200
65
54
45
38
32
17
14
12
10
9
250
65
54
45
38
32
16
14
12
10
9
300
64
54
45
38
32
16
14
12
10
9
Mean Value
65
54
45
38
33
17
14
12
10
9
Table 18: Absorption Values for Seawater and Freshwater at 400 kHz and 200 kHz
2
Equation used for computation is from: Ainslie M.A., McColm J.G., “A simplified formula for viscous and
chemical absorption in sea water”, Journal of the Acoustic Society of America, 103(3), 1671-1672 as employed
on the NPL website, op cit.