Ambient Noise Measurements with an Acoustic Submerged Buoy in Deep Sea

An acoustic submerged buoy moored at the ocean bottom was applied for an ocean experiment in deep-sea area. This submerged buoy consists of a vertical optical-fiber acoustic sensor array and a cross array of fiber-optical vector sensor, 32 channels in total. In addition, there were four underwater signal recorders suspended at different depths along with the submerged buoy. All these sensors were approximately deployed to the depth scale from 4000 to 5000 m. Spectral analysis results of the recorded ambient noise are mainly concerned and discussed in this paper, which includes the time-varying and statistical characteristics of noise level at the frequencies of 100, 200, 500 and 1000 Hz. Furthermore, an attitude analysis method for the submerged buoy is presented by using amplitude fluctuations of low-frequency ambient noise spectra (< 100 Hz). It is shown in the data processing results of the sea trial that the regular motion of the submerged buoy system caused by ocean currents can be embodied clearly with this method.