Study On Backward Scattering Intensity And Marine Environment Noise Of Acoustic Volumes In Arctic Ocean Pacific

The Arctic underwater acoustics becomes a new hot in research work. Based on the investigation during the Sixth Chinese National Arctic Research Expedition in summer 2014, the characteristics of volume backscattering strength and marine environment noise in Pacific sector of the Arctic Ocean are analyzed. The main points of the dissertation include:(1)The volume backscattering strength(Sv) measured with Lowered Acoustic Doppler Current Profiler(LADCP) from the Bering Sea indicated that the vertical migration exist in deep scattering layer. The volume backscattering strength under1000 m depth has a maximum at about 1800 m depth.(2)Sv under the open water(ice concentration<15%) is significantly higher than that in seawater under the packed ice(ice concentration>50%). Ice melt causes increasing of opaque creatures and suspended sediment, and leads to increase of Sv.According to the characteristics of low Sv under the packed ice, the proposal about the parameters of LADCP setting is given.(3)Sv in the Chukchi Borderland is significantly higher than that in its surrounding waters. In polar day, the vertical migration of scattering layer is related to the local solar altitude angles.(4)Sound from the deep scattering layer was measured. The frequency of sound signal is between 2000 Hz to 3000 Hz.(5)Sampling sound of bottles installed in SBE-911 CTD is extracted with a filtering method based on wavelet transform with variational threshold.Time-frequency property of sound signal is analyzed. Sampling sound of bottles in time domain is composed of signal of releasing trigger and closing bottle cap.Sampling sound of bottles in frequency domain has a bimodal structure. The peak values of frequency are 750 Hz and 2300 Hz. The significant levels of bimodal structure and pulse volume in time domain are relevant.