  We investigate the question whether there is a real difference in the light
change between stars classified as semiregular (SRV) or irregular (Lb)
variables by analysing photometric light curves of 12 representatives of each
class. Using Fourier analysis we try to find a periodic signal in each light
curve and determine the S/N of this signal. For all stars, independent of their
variability class we detect a period above the significance threshold. No
difference in the measured S/N between the two classes could be found. We
propose that the Lb stars can be seen as an extension of the SRVs towards
shorter periods and smaller amplitudes. This is in agreement with findings from
other quantities which also showed no marked difference between the two
classes.
