🚀 go-pugleaf

In article <3305@kalliope.rice.edu> phil@Rice.edu (William LeFebvre) writes:
>In article <862@m3.mfci.UUCP> colwell@mfci.UUCP (Robert Colwell) writes:
>>...
>>Solving that for N in seconds, I get 0.27 seconds.  My impression was that
>>the booms were obviously separated in time.  I'd expect that people might
>>have a hard time distinguishing booms that were only 0.27 seconds apart.
>
>I'd expect that you're wrong.  That's a quarter of a second, which is most
>certainly distinguishable (or for you computer types:  250 milliseconds).
>Being a former percussionist (you know, one of those guys that plays
>drums), I remember routinely playing notes on a snare drum that are a
>quarter of a second apart (four notes per second).  Believe me, the notes
>were quite distinguishable.  Or don't believe me.  But if you don't
>believe me, do the following experiment:  tap the countertop once a second
>(use your watch to time them).  Double the rate, then double it again.
>Quite distinguishable.  And in fact, about the same rate that the
>shuttle's booms are heard at.

If the craft were really travelling at 300mph, there wouldn't *be* any sonic
booms.  It has to be travelling at over twice that speed to even generate
the booms.  So the arrival time difference between the booms (if they exist)
from the front and back of the craft would actually be at most 1/10 of a
second.  If the front/back explanation is right, (and I don't dispute that
one can hear sonic events separated in time by 1/10th of a second, I just
wonder if the attack portion of the boom's sonic envelope is sufficiently
sharp that a second one 0.1 seconds later would be obviously distinguishable)
then why don't all supersonic aircraft generate this same phenomenon?  I was
under the impression that the craft had to be sufficiently fast to have this
occur, and that it happened with the shuttle because it was going umpteen
zillion mph at the time, much faster than normal aircraft can achieve.
(Ok, the front/back explanation would hold up better with longer aircraft;
is the shuttle one of the longest supersonic aircraft?  I would have
imagined a B-1 to be much longer).

Bob Colwell               ..!uunet!mfci!colwell
Multiflow Computer     or colwell@multiflow.com
175 N. Main St.
Branford, CT 06405     203-488-6090