I've had this happen a lot of times...I prefer working on little things alone or atleast with an assistant that is quiet, maybe the ocassional conversation, and hands tools to me if I am unable to get them.

The best way to avoid them is to completely hide under your car
Also the random expletive shouted at a volume that could be heard two blocks away helps keep soft ears away, but we have young ones next door to think of

Another good solution...start a fire and stomp it out...generally that makes my friends much more uneasy about being near me