Hi,
First do test your AC adapter using a multi tester and see if it's supplying the correct voltage to power or charge your laptop or if you have another AC adapter that has the same voltage do try it and see if the same problem will persist because if not that means it's your AC adapter that is faulty. I would recommend to stop using it since it may cause more damage in the long run of using it. Next is to try to boot up your laptop without the battery and just connect it directly to the AC adapter then observe if you'll still hear that static sound. If the same scenario will happen I would suggest replacing the AC adapter already.