okay I'm having some issues with my Chevy Cobalt the back brakes was rubbing so I change the break shoes assuming that would make the noise stop.that stop the grinding noise but I can still hear

a humming? from the brakes? never heard brakes humm. assuming you had rotors turned if needed, new pads installed correctly (with any shims and clips involved) and you tightened your calipers good they should be fine and it may not be the brakes at all. if they were binding up before then you may need to replace the calipers or rebuild them and bleed the system. your e brake may need to be adjusted also. think though if they were sticking that can affect everything in the drivetrain. it will increase stress on the transmission, motor, u joints, rear end. drivetrain noises can be hard to pinpoint. check your rear bearings. put the rear of car on jackstands and put it in gear and let it idle. walk to the back and listen. a rearend will sometimes 'howl' before it goes out. the noise normally increases with speed. check all the simple things and work your way up to the bigger stuff. good luck. hard to tell u much wo hearing it.

And always take advice from people who think Cobalts are rear wheel drive with a grain of salt. The rear calipers are likely seized and need to be replaced. Could possibly be rear wheel bearings as well. The mechanics at the rear of a Cobalt are pretty simple. There's not a lot else back there to make noise. Also a faint rubbing noise is normal. If that's all you're hearing and as long as nothing's getting super hot, you may not have a problem at all.

Ok, if the cobalt has rear disc you might have debri in your parking brake! If not then I would suspect faulty installation, warped rotor or drum! If you have more than 70k suspect bearings also!