1-The ball cock is inside the toilet tank to refill the tank after the
2-Tank flapper/bulb / stopper is lifted (VIA handle) off the Douglas valve ( the thingy that allows the water to actually flush the bowl)
3- Even NEW faucets could have a defective (loose) washer.
Try each faucet first one side (Hot) then Cold to see if you hear the noise
You may look into the possibility of installing an air chamber to take up for the shock waves that can occur from quick closing valves like the solenoid valves in your washing machine or dish washer.
Try to find your main pressure as excessive pressure would also cause a banging ( THUMP)
Have any more questionsplease feel free to ask . Have a great week end
Sylvan (Life Member DAV) USN LOL