Noises Make me Uneasy

My boss has this habit of muttering things when he is frustrated or angry or even just trying to figure something out. He also hisses swear words very sharply (e.g. shhhhhitch or damn itch).

Yesterday he completely stopped using words and started making this growling noise. Now, I have heard this exact same noise before. It came from my keeshond (a medium sized very furry dog) when I was growing up. It meant, "I will not move from this spot and don't you dare try to pick me up and make me."

I have no idea what it means coming from a human being.