I followed this steps once again and problem sorted.
1) System Restore,
2) Safe Mode with Networking, but I am getting same problem in Safe Mode as well and static sound (irritating although mute key is on)
3) Unplug all USB devices.
4) Update Keyboard driver,
5) Scan Laptop with Antivirus & Antimalware but nothing found.
6) Reset keyboard Settings.
Thanks for all your advise.