My cat comes indoors and night into the kitchen and I swear she is shouting hello. Well, it's more like h e w o. It is very eerie to say the least.
I think you are describing what we in our household call a "purr-meow." When a cat is happy you're about to feed her and is purring in anticipation, but is wishing you would hurry up, they can do this neat-sounding throaty b-g-r-r-o-oow that is half purr and half meow. Evidently (from research they have don on pets and their owners), it is a very effective sound, getting the person's attention about 100% of the time.