The invention relates to a pipeline 1 moving effluents at seabed level and comprising an inner shell 3 and at least one outer shell 2 which is separated from the inner shell by an annular space 7 receiving an insulating layer 4. A storage stores received signals acquired through the transmission and reception. The result of the correlation represents a channel model as affected by echoes within the channel, and then a second vector of data is added to it to derive correction information useful in positioning moveable filter taps to suppress the most prominent echoes. The spacer also includes a second mounting surface substantially parallel to the first mounting surface and located on an opposing side of the spacer from the first mounting surface.