ipod touch 4th generation 8gb will not connect to itunes

Every time I plug it in to the computer it doesn't make the usual 'connection' sound, but rather a deeper sound that indicates it's not connecting correctly.

I know it's not my ipod, because I have connected it to an ipod circle speaker dock and it connects and charges/plays music just fine.

My itunes does work, but it doesn't sync the ipod or even recognize it.

I've tried two different plugs from the ones I normally use to connect it to the computer, as well as tried two different places to plug the USB in to.

It's been acting like this for a week or so..please help!