Hmmm, Penny: my engineer's antennae (admittedly somewhat rusty, now) cry "BS". I, too, have heard the story from those who were there at the time (my parents), but I am sceptical none the less. Either the German engineering was inferior to ours or ours was so much inferior to theirs that the English bombers' engines were so wildly off-synch that their beating was too rapid to hear. Both of these sound unlikely to me.

I remember, long ago, my physics teacher (also there at the time) saying that it was an urban myth (or words to that effect).