An analysis of large-scale variations of noise storm intensity and frequency spectra has been carried out basing on IZMIRAN dynamic radio spectra compressed in time. It is shown that various enhancements and weakening of noise storms as well as changes of their frequency spectrum appear to be caused by effects of coronal mass ejections on sources of the emission or/and electron acceleration in the corona.

                          (d) 27.06.1999 ;    (e) 29.04.2000 ;   (f) 30.04.2000 ;