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REPUBLIC OF SERBIA MINISTRY OF DEFENCE
MINISTRY OF DEFENCE Material Resources Sector Defensive Technologies Department
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WAVELET ANALYSIS RADIATED HYDROACOUSTIC
NOISE OF FEW
MIODRAG VRAČAR Military Technical Institute, Belgrade, vracarmiodrag@open.telekom.rs
Abstract: Wavelet analysis is a special technique of signal analysis with variable time sized regions. Therefore, wavelet analysis allows using long time intervals when it is necessary to obtain more precise information in low frequencies domain, and shorter time intervals when is interest to find out high frequency content of the signal. Noise in water that produces ships and other navigable objects is of special interest in case when navigable objects are military. Frequency band of such hydroacoustic noise is in wide limits starting with low frequencies, lower than 20 Hz, which originate from hydrodynamic process when ship’s hull is moving through the water, and goes to high frequency limit of few tens of kHz due the cavitations process at the ship’s propulsion propellers. Such hydroacoustic noise signals are non-stationery signals and continue wavelet transform, or discrete wavelet transform, as computational efficient technique for extracting information about non-stationary signals, is used to analyze radiated hydroacoustic noise few type war ships. Keywords: discrete wavelet transforms, hydro acoustic radiated noise, war ship. |
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