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3 Hydroacoustics

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The one – third – octave spectrum as a method of vessel identification

100%

Gloza I. , Józwiak R. , Buszman K.

2014

tom Vol. 17

63--68

The subject of the examinations carried out is hydroacoustic noise in coastal zones. Under these conditions natural noise and the noise from moving vessels affect each other, as well as interference from industrial infrastructure located close to the coast. Both natural noise and noise caused by human activity affect the detection and identification of noise sources in these conditions. Experiments have been performed by the mobile measuring module in the Gulf of Gdansk. This showed that it can extract spectrum components, based on the results of underwater noise. These components allow the detection of moving objects. The collected database of measurements enabled the comparison of one-third-octave spectra of three different ships. The components specific to the type of vessel could extracted as a result of comparison. Consequently one of the three tested vessels could be identified.

Uncertainty analysis of the determination noise source direction using the tetrahedron hydrophone array

100%

Gloza I. , Józwiak R. , Pawlik P. , Bartko W.

tom Vol. 18

59-68

The analysis of the uncertainty of the determination of the noise source direction in the aquatic environment is presented in this paper. The type A uncertainty of the bearing algorithm was determined on the bases of multiple measurements of the hydroacoustic pressure by means of the TC4032 type hydrophones and the GPS device data. The influence of the non-linearity of the amplitude-frequency characteristic on the uncertainty of the determination of the noise source direction, was also described. The influence of water density, electromagnetic disturbances and irregular noises on the final uncertainty was determined. On the bases of the determined uncertainty components the uncertainty budget, of the determination of the angle showing the direction from which hydroacoustic waves are coming, was prepared.

Data compression and clustering of one-third-octave spectra by acoustical colors

100%

Józwiak R. , Nissen I. , Listewnik K.

tom Vol. 20

85--92

This article presents a new approach for the data compression and clustering of one-third octave spectrum by using "acoustical colours". Using in-situ measurements by the IGLOO – sensor nodes it can show that this approach allows a clustering of the colors for a quick look classification. This is helpful using wireless acoustical transmissions with restricted transfer volume in underwater sensor networks without jamming their own measurements.