17" Powerbook-Speakers Sleep?

[Benn]

Yesterday I got my 17" powerbook.  This thing is incredible--definitely 
the coolest portable ever.

One of the first things that I've noticed, though, is that the speakers 
seem to sleep... Example, with no music or other sounds playings, I get 
an IM.  Just before the IM sound comes, I hear a sort of pop from the 
speaker, then the sound plays.  If I'm continually sending and 
receiving messages, it's fine, but if there's some pause, it'll do that 
again.  Is this normal for the 17" powerbook?  have others also 
experienced this?

Benn