Abstract: We consider a new scenario in blind speech separation problem in which the number and the features of active sources change with time in opposite to the previous methods in which all sources are active all the time. Accordingly, we propose the new DESICA algorithm for source separation which is a compound of the ICA and DESPRIT algorithms. In this algorithm, using the ICA, the separation process is performed initially and then using the DESPRIT algorithm, the binary mask of silence intervals is calculated. Finally, by applying the binary mask to the separated signals, the final separation is obtained. Simulation results show that the DESICA algorithm improves the SDR and SIR about 6dB compared to those of the DESPRIT algorithm. Also, the SEN is improved about 11 and 17dB with respect to those of the ICA and DESPRIT algorithms.