Is it normal for a parakeet?

i have one older and 2 young parakeets, and when i play wih them (only one at a time) i try to teach them words. but after repeating it looks like they are trying to say something, like there beaks are moving, but no sounds comes out(kinda looks like its mubling to its self). the younger ones always do really load yells and calls and the older (which is in a different part of the house) only yells for you to come and play with him. so are they trying to find the right ket to say the words or are they just crazy? haha