The understanding of the origin of self-excited pressure oscillations in technical combustion systems as well as a successful design of pulse combustors depends on the knowledge of the dynamical behavior of the used flame. In this study the mixture mass flow rate through the burner nozzle was modulated sinusoidally to measure the frequency dependent heat release rate of a premixed turbulent jet flame. The dynamical behaviour of the investigated flames was found to be predominantly a function of a Strouhal number formed with the characteristics of the corresponding steady flames and to be very similar to that of an ideal idle-time model. The discrepancy between this model and the experiments at higher frequencies could be explained by the periodical formation of vortex rings.