Measurement of sound absorption in low salinity water of the Baltic Sea

Shallow water propagation measurements in the thermocline–halocline refractive sound channel of the Baltic Sea are utilized to estimate the absorption coefficient in low salinity water of 8 ppt (8.0 pH, 4 °C) for 0.5–10 kHz. The lower margin of the present data which are derived from transmission loss by subtraction of cylindrical spreading can be represented by the Francois and Garrison formula of 1982. However, measurements of the boron relaxation frequency indicate that this agreement does not necessarily support the assumed salinity dependence of the relaxation frequency but might be produced by appropriate scattering loss of the refractive channel.