Low Static Sound within my iMac Gets Recorded Through LP 9

I'm hearing a low churning crunch sound within my iMac. I guess that means my hard drive is about to die. Unfortunately that low static sound get recorded on Logic Pro 9. Other than taking the iMac to the Apple Store for a look over, any other advice. Same thing happens on GB, and it's not the Mic connection. I hear that crunchy sound when I turn my iMac. Thanks for any help