A bullet bow shockwave is a physical and audible wave created in the air when a bullet only travels supersonically faster than the speed of sound.
The bullet bow shockwave is the result of air being greatly compressed at the front-most tip of the bullet as it slices through the air. As the bullet moves forward a broadening wave of the compressed air trails out diagonally from the bullet tip and all sides of the bullet sides creating a conical waveform. This conical waveform may be audible to a witness as a whip-crack sound.
A bullet bow shockwave can be heard by any witness as long as the bullet speed is faster than the speed of sound, whether the bullet was fired from a weapon giving off an openly audible muzzle blast, or a mechanically-suppress-fired muzzle (silenced weapon) blast. If a bullet is fired from a silenced weapon, a witness can mistake the bullet bow audible shockwave whip-crack for the weapon muzzle blast audible wave, which is a separate, slightly preceding, audible event. I might be noted here that if one incures such an event, that the sound you hear from a silenced weapon will not be from the point of origin. This crack sound will nost likely be 180 degrees opposite from its origin. The sound will come from the point that the bullet ceases to be faster than the speed of sound.