I'm new to chickens as well, and I got my first bunch in March.. and unexpectedly- I got 3 more sets of chicks all different ages.. 3 wks down to almost 1 week. What I did when I mixed them, since I was afraid of the newbies getting picked.. I took EVERYONE out of the brooder.. cleaned it out, new food, new water, and then put everyone back in. One older chick, one new, one older, one new... until they were all in. They honestly looked slightly confused- but happy to report NO altercations! When I had to put the next batch of younger ones in, I took out the more active older ones, and put them in a seperate brooder of their own. Each time I've used this method, it really seemed to work. I think your loud mouth will quiet down once there's more company- or not!! I have one that wouldn't shush unless he had a visual on me or my fiance!! He's 3 weeks, and it HAS stopped, but he still looks for us!!