My cat meows when outside the room I'm in. She acts like she's lost in the middle of nowhere if she can't physically see anyone and thereby must repeatedly meow as loud as possible in order to be rescued. Doesn't matter if she was just on my lap and I haven't moved. She leaves the room and is suddenly lost. The second I call for her she runs to me following the sound of my voice and then is perfectly quiet, cuddly and all purrs.

If he's anything like my cat, anything and everything, sometimes just to announce where he is.

If he misses bathroom time before bed he goes in front of the bathroom and puts his head up and howls.