new keyboard spacebar has odd sound

I just got my new iMac yesterday and have found that all keys sound the same apart from the spacebar which sounds like plastic is underneath each time I hit it, very annoying, could it need replacing or cleaning under the key.

I have searched the forum where people say the spacebar is loud but nothing about odd noise. Also says you cant take off the key otherwise you void warranty which is a bit worrying...

Thanks for the help
Scott