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channel for the acoustic transmission of digital data acquired by seismic instruments on the seafloor to a
moored buoy. The acoustic link will be assured by high frequency acoustic modems operating with a central frequency
of 100 kHz and a band pass of 10 kHz. Since the maximum depth of the sea is about 300 m and the
planned horizontal distance between the seismic instruments and the buoy is 2 km, the acoustic data transmission
shall be near horizontal. In this study the signal-to-noise ratio is plotted against depth and distance from the
source, thus defining the limit after which the transmitted information becomes unreliable. Using ray-theory, we
compute the amplitudes of a transmitted signal at a grid of 21×12 receivers to calculate the transmission loss at
each receiver. The signal-to-noise ratio is finally computed for each receiver knowing also the transmitter source
level and the acoustic noise level in the Gulf of Naples. The results show that the multipath effects predominate
over the effects produced by the sound velocity gradient in the sea in the summer period. In the case of omnidirectional
transmitters with a Source Level (SL) of 165 dB and a bit rate of 2.4 kbit/s, the results also show that
distances of 1400-1600 m can be reached throughout the year for transmitter-receiver connections below 50 m
depth in the underwater acoustic channel.
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