Are shock fronts always present in pressure waves radiated by cavitation bubbles?

Oscillations of cavitation bubbles can be extremely intensive. During these intensive oscillations narrow steep pressure pulses (spikes) are radiated, the peak values of which are very high. In the literature it is common to refer to these pulses as shock waves. But are these pulses really always shock waves? Shock waves, such as those generated in shock tubes or at underwater explosions can be characterized by a very steep shock front which propagates with a supersonic velocity [1]. However, when we have examined recently recorded pressure waves radiated by spark generated bubbles with an aim to find the shock fronts in them, we were surprised at not finding fully convincing proofs of the shock fronts presence in these waves.