Jack makes this Yawning sound when he is irritated with us for not showing him enough attention, or if I'm not fast enough to take him out…..It used to be just a morning stretch thing, but I started praising him like crazy, and now he does it to talk to us. He did it once while I was on the phone with my mom, and she was seriously alarmed trying to figure out what it was.
The other funny thing is that Jack never barked until we went for Christmas to my sisters. She has a big dog and my parents dog was there as well....both barkers....after we came back from there, every once in a while he will let out one short bark.
So, from that, I think that praise and the example of other dogs can maybe encourage the noise-making tendencies. Although, just like people, if a dog is a quiet dog, it probably won't matter how many singers you get them around, they probably won't get there.