The connecting/disconnecting sound usually indicates that you either 1. have a bad charging cord, or 2. the charging port on your phone has come loose.
First, try a new charging cord, and see if this solves the problem. Note that when a battery goes completely dead, it can take some time (up to 15-30 min). I also suggest plugging the phone into an electrical outlet instead of using the USB port on your laptop.
Second, if after charging for an hour with the new cord in a wall electrical outlet doesn't work, slightly wiggle the cord in the charging port of the phone. Can you see the port moving? Does the phone seem to charge when you move the cord and hold it in a particular location/direction? If so, the solder joints of your charging port have cracked. You have two choices: 1. find someone to repair the phone (either micro-soldering the port or replacing the entire PCB assembly), or 2. replace the phone.