[Potironette]

There's a whole lot more factors to sound than I'd thought :o.
By sound reflecting, do you mean that when someone knocks on a door, the door also knocks on the person's bones and then the person's bones make the reflected sound..?

I have heard of cold welding from class! But it was put in as an interesting side note and I forgot how it happened and didn't connect it with friction. But I'd though it only happened in space o_o