Alzheimers and dementia patients always respond to their environment. So, the problem here, most likely, is that your unit has become too stressed and chaotic for these people to deal with, too. So, they respond in the ways you are describing. It's going to be your goal and challenge to figure out what is agitating and stressing out your unit. Do you have an aide who is being too rough? Do you have an aide who isn't trained in how to treat these folks so he/she is demeaning to them and they are upset? Find the problem, whatever it is. Are your patients just picking up your own stress and mood?
Start by lowering your own voices. Walk slowly and relaxed (yeah, that's a stretch when you are stressed yourself, but try it anyway). Put on quiet mood music. Get activities to come in and do some exercises with them to use up some of their own energy. Take a bread machine to work and bake bread because the smells or "home" will often quiet them, and you can also feed them the bread when done, and deal with weight loss, too. The point is that YOU are reacting to the problem instead of finding interventions FOR the problem!