According to the excellent web site www.v2rocket.com
A description of a V2 impact would be as follows.
First, a whip cracking sound of a blast wave created by the rocket (moving faster than the speed of sound) bounces off of the point of impact just split seconds before the flash of impact. This was followed by the chaos of the explosion with debris and earth churned skyward. Soon, the whine and rush of whistling air as the sound catches up with the rocket followed by a deafening roar of the incoming rocket, which tapers off to silence. There could be no warning. The V2 impacted at 3 times the speed of sound.
(Quote courtesy of and used with the kind permission of Tracy Dungan www.v2rocket.com)