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.