Internal Sound within my iMac affects recording

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. other than taking the iMac to the Apple Store for a look over, any other advice. Same thing happens on Logic Pro, and it's not the Mic connection. I hear that crunchy sound when I turn my iMac. Thanks for any help