I have an aunt (twice removed if I'm telling the story) who sounds like her gene pool needs some chlorine (she's related by marriage in some way). She says "yah" a lot.
"Yah, it's Jo and Tom. Yah, just leave a message and uh, we'll call ya back, yah." It's generally accompanied by snorting and scratching sounds, which makes me wonder if she's got pigs living with her.
All done in a flat, nasal Wisconsin twang. I've got the heebie jeebies just thinking about it.