Usually when disconnecting and then reconnecting the battery, you may blow a fuse. Check your fuse box for any blown fuses.
Be sure to check if your radio is not on mute, or that the volume is turned all the way down.
Also, see if your radio has any tuning options. There may be something adjusted all the way down.
Try inserting a CD or cassette to see if there is still no sound present.
If none of these things help, then call your dealership to see if your vehicle has a Stock Amplifier. The stock amplifier could have gone bad and may have to be bypassed.