Thank you for the replies. The noise is heard at opening and at shutting the faucet. Nothing is heard while water is running. As for the draining the pipes, it indeed made it worse, but I read it right in this forum. Here is a copy of the text:
"You can make your own knock valve. All it consists of is a dead end piece of pipe oriented vertically so air stays trapped in it. It acts like a spring to cushion the shock of the water suddenly stopping. It should be located near the end of the run (near shut off valves). Before you go to all the work of installing these, try shutting off all the water in the house and drain all the pipes. Doing this allows air back into any anti knock valves that may be there. When you turn the water back on, the faucets will hiss for awhile, until the air is expelled."
So, I will research about the water hammer and hammer arrest to see what people are doing about this. Thanks for the replies.