Sunflowerzz - This is for a longarm machine, but Amy does a great job of explaining what and why:
http://www.youtube.com/watch?v=QpcnAHeJP4s&feature=c4-overview&list=UUyHs2O8pXagQrQ-xm6ssu5QET
<a href="http://www.youtube.com/watch?v=QpcnAHeJP4s&feature=c4-overview&list=UUyHs2O8pXagQrQ-xm6ssu5Q" target="_blank" rel="nofollow">
http://www.youtube.com/watch?v=QpcnAHeJP4s
ETA: There's more than "noise reduction" going on in the box on your machine. The video says that it's mostly for noise reduction and that's true for an APQS machine, they have anti friction stuff built in - PTFE maybe? The older domestic machines are a little different. The priciples are the same though and she goes into detail than I really want to type.
