Do Lobsters Really Scream When You Boil Them?

I have heard many people make the statement that they don't want to cook lobster at home because the horrific sound of the lobster screaming. What are they talking about? Do they really think that a live animal would scream when put into a tub of scalding hot water?... Well I guess I see a little bit of their point. But the truth of the matter is that lobsters don't scream when boiled. In fact that's impossible because lobsters don't have vocal chords or any other means of vocalization. So what is that weird high pitch sound that sometimes is heard when a lobster is boiling? It is simply the sound of a lobster's exoskeleton and musculature tightening up and releasing gases under the heat of the boiling water. Makes sense, I guess.... Anyways, All I really know is that some lobster dipped in butter is one of life's great pleasures. :)