EVOLUTIONARY SPECTRA OF NON-STATIONARY UNDERWATER SOUND REVERBERATION PROCESS

<正>In this paper,we discussed the underwater sound reverberation of moving medium,which is anon-stationary stochastic process even after compensating its energy attenuation.Evolutionaryspectra is introduced,and the non-stationary properties are described by a non-stationary factor anda characteristic width.We assumed that the Doppler shift is a stationary normal process or a normaladditive process and obtained the evolutionary spectra.After compensating the energy attenuation,a non-stationary sound reverberation can be expressed as a product of a deterministic time functionand a stationary stochastic function.The bi-hump in power spectrum is due to the non-stationarityand the non-homogeneity of the medium motion.When we use the estimation ν.i.e.the meanDoppler shift of a stationary process to estimate the mean Doppler shift of a non-stationary rever-beration process,the estimation ν is a biased one.