All demand pumps are noisy, some more than others and some sound like a mini-jack hammer, especially if not mounted correctly.
I do NOT agree that you should not make use of your warranty and you SHOULD ask the dealer about it. They deal with this stuff all the time and probably can tell you with a quick look and test if what you have is "normal" or not.
I eventually got tired of hearing mine chatter and had the pump replaced with a variable speed model. If you run the water slowly, it is almost silent. Higher flows still make some noise but nothing like the old one.