Orval Fairbairn wrote:

In article . com,
"Carsten Nielsen" wrote:

At one of the reentries, the TV commentator mentioned a sonic boom.

I can't remember if it was double.

It should have been a single boom, as the Apollo craft was a single
surface exposed to hypersonic air. The double boom we hear from the
shuttle is due to the fact that the nose, wings and fin all create their
own, separate shock waves.

http://www.jsc.nasa.gov/history/oral...CS_4-16-01.pdf
Page 15:

John Stonsifer about the situation aboard the recovery ship:

"But the first clue we always had was the sonic boom,
because when Apollo came back in,
it was coming pretty much over the landing area,
almost straight down,
and you knew when you got that "boom, boom"
we'd always yell "It's overhead".
So then we began to really start lookingfor it."

--
Jürgen Kozlik