Chris Albrecht of GigaOM interviews Bill Byrne of google about the "biddy-biddy-boop" sound developed for the 800-GOOG-411 phone directory service.

gigaom.com/2007/11/10/goog-411 ...

Here is an mp3 ogf the sound.

goog411.googlegroups.com/web/1 ...

Here are some slashdot comments.

slashdot.org/article.pl?sid=07 ...

Here is a wma of a goog-411 halloween sound reported by "13 ideas".
I wonder if they will have other holiday sounds.

geocities.com/blog_13ideas/goo ...

13ideas.net/2007/10/31/goog-41 ...

First sound link doesn't work

It works for me. It is a background sound, so you may want to raise the volume.