This has happened to me, too. Students will giggle over one of Raphael's
beautiful infants or a Degas bather. I simply comment on the innocence and
artistry of the work. They'll giggle over underwear ads in magazines we are
using for projects, too! I usually tell them simply that I don't have time
to censor anything that will make them laugh--it's too vast, and that if
something embarrasses them, to simply turn the page, and not gather their
neighbors about them for a group giggle. I try not to focus on this for too
long. I don't gather the books or magazines and put them away either. Just
a matter-of-fact dialogue.
Argh! Adults are another matter. I live in the mid-west and heard the
thump you described!