Attenuation of ship noise line-spectrum caused by the randomness of ocean channel

The universality of quasi-periodic random sound pulse sequence ship noise model is elaborated.The focus is on studying changes of line-spectra produced by quasi-periodic random sound pulse sequence after transmission in random inhomogeneous ocean channel.It is pointed out that under most working conditions,ship noise is not the superposition of several different frequency additive sine waves and the broadb and continuous spectrum noise directly,but is a kind of signal itself without containing any limited strength additivesinusoidal components.It is shown that the ocean channel multipath effect causes time delay extension of shipnoise pulse sequence signal,and the random inhomogeneity of the ocean channel makes the quasi-periodicity downturn of ship noise random sound pulse sequence signal,and can lead to ship noise line-spectrum "extra" attenuation.For the ocean channel with a wide range non-uniform watermass,the random inhomogeneity of water medium can cause ship noise line-spectrum "extra" attenuation of up to 11 dB on the propagation distance of 50 km.