Análise da refletividade do sinal acústico pelo fundo marinho no espectro das comunicações submarinas

Abstract

The development of an efficient underwater communications network that allows data broadcast in a safe and reliable channel for long distances into the oceans has been an ongoing challenge considering the physical and environmental parameters. The geoacustics supports a better understanding of underwater communications since it studies the sound wave propagation behavior as propagates through the medium, leading to: velocity, phase, frequency, and amplitude variation, which can be correlated with medium characteristics. In this thesis, as a small contribution to a better understanding and improvement of these tools, some correlations were acquired after a sub bottom profile (SBP) amplitude analysis to achieve, by inversion, the bottom physical properties. To develop this study 250 km of seismic investigation and 27 bottom samples were computed to associate sea bottom physical properties with acoustical properties. The 27 samples were straightly correlated to the mean amplitude value from the seismic ping to achieve an equation that was used to transform the seismic data in physical characteristics for the entire seismic profile. The main parameter used to correlate the data was the acoustic impedance, the result from bulk density and sound velocity of the medium that were identified at the site of the study, and the amplitude of the acoustic signal recorded at the transducer for the bottom envelope. The result was a good correlation between the physical and acoustic parameters (R²= 0,9 for sandy materials from Shepard’s classification and R²= 0,9 for litoclastic samples according to Larsonneur’s classification), allowing the construction of a faces map from seismic data.