My Yorkie has never been able to make any noises other than barking, screaming, and growling. She doesn't whine or whimper, but makes a very quiet sighing/hissing sound in her throat when she's upset. You can't hear it unless you hold her near your ear. She also makes a funny "roo roo!" sound when someone comes home and she gets excited.

She's a tiny dog and was the "runt" of the litter, so I've always wondered if there was something wrong with her throat. Does this sound abnormal?