Multibeam bathymetry systems use the travel time of acoustic
pulses as observable to determine the depth of the seafloor. In
order to provide appropriate echo quality necessary for depth
determination and seafloor shape recording, a high acoustic
source level is needed. The main factors affecting the sound
level of the emitted sonar pulse during the travel through the
water column are geometrical spreading, absorption and the
backscattering strength of the seabed. The reception threshold
of the acoustic receiver determines the sound level needed to
detect the acoustic pulse. Common deep sea multibeam systems use
the determined depth as an indication to control the source
level necessary for the successive ping.Lowering the
transmission level of hydroacoustic sources is a general demand
to reduce the impact of sonar signals on the marine life. In
order to protect marine mammals we studied the capability of RV
Polarstern's Hydrosweep multibeam system. However, reducing the
source level finally limits the abilit