short bursts are actually only a small fraction, which is above the background noise, of long bursts. We have already seen that the noise cause us to loose pulses. Is it possible that a long burst with a single dominant, very intense pulse, (or a group of very close and intense pulses) will loose all its structure, apart for this intense pulse, due to noise and become a short burst. Fig. \[flux ratio\] rules out this option. It depicts the counts ratio between the most intense pulse and the second most intense pulse within long bursts. The graph shows that in 32 out of 34 bursts the second highest peak is more then third of the most intense peak and in 27 bursts the second peak is more than two thirds of the first. The noise cannot cause one pulse to disappear without the other. As these two peaks are usually separated by more than two seconds, the noise cannot convert a significant fraction of long bursts to short ones. Clearly the noise has some effect on the duration histogram and in a few cases the added noise converted long bursts into a short ones, but it certainly cannot produce 