Barking - help needed

[Kaytlin and Cooper]

so, we moved into our apartment yesterday, and Cooper has started barking. At everyone walking past, at every noise in the hall way, at every other dog barking. She even growls sometimes - not aggressively, but its still a growl and it is unacceptable.

We have lived in shared houses before (2 other suites) and she never barked. Then we lived in the country with the inlaws for 7 months where there were no noises from other people. is she just getting used to the noises again or is this going to be a habit? 

Thankfully everyone here is very nice, most have dogs themselves (some who do bark at every noise) but I dont want this to become a problem

Thankfully Im home most of the time at the moment so I want to stop it now before it becomes a habit. what is the best way to go about it? I do have an air purifyer which gives background noise but it doesnt seem to make a difference

[Suzann, Rosey & Bandit]

I had to use a bark collar on Rosey, it worked and now she doesn't need to wear it all the time, but after many training attempts it was the only thing that works.

[Nelson, Rufus & KO]

We have a Citronella collar for Rufus. After the first 3 or 4 times, we didn't even have to fill it. We just put it on him and he stops..

[Kaytlin and Cooper]

Yesterday was much better. Whenever Cooper barks I get up and go to where she is. I say "its all good" (ok is her release word so I didnt want to use that in a phrase). If she barks again I pat her on the head and say "enough". If she barks a third time I use the "uhuhuhuhuh" sound which she knows means "no dont do that". That seems to be working. I have yet to get a can - that is on the list for today.

[Lori, Rooney & Zuzu]

I have been really interested in this thread because Rooney (five months old) has just started doing what I call "alarm barking".  He does not bark at every noise or person at all.  In fact, he seems to be quite selective about what raises a red flag for him but none of his choices have been alarm-worthy in my opinion so I'd like it to stop. I do not have the slightest interest in Rooney acting as any sort of "watchdog" for anyone so I want to discourage this behavior.  I think I'm going to start with the patting on the head and "enough" and see if that helps.