R2Sonic 2022, Operation Manual

Page: 108 / 133

Page 108 of 133
Version 3.0 Rev r000
Date 25-08-2010
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 10: 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.