What can't sound travel through?

in space, no one can hear you scream... if the space is a vacuum

CyanJaguar62, think about sailors tapping out sos metal against steel underwater in a submarine or huge ship to let rescuers know they're trapped...it works.

Player #119530601, unless the maid was vacuuming

This is not a very good explanation in my opinion. The last sentence just says the same info.. that sound does not travel through a vaccum.Big deal!

Player #119530601, it does. I was a sonar man on a frigate in the Navy. We used the sonar to get our way if the engineers were putzs. We’d give them a 7 second pulse at midnight to wake them up of course we couldn’t use the sonar for 24 hours before we could use it again because it would shut off. Then we’d just use passive sonar. Once in a great while, we would use the an/sqs-35 fish out of the back of the ship. That was before Ensign Hymen rammed it into an undersea mountain and dragged along the top. When I pulled it up, all that was left were a couple of circuit boards and pieces of the fiberglass fish. I told my supervisor, he told the OOD, who told the Captain. Ensign Hymen got yelled at so much and so loud and so long, everybody heard the Captain. We hardly ever used the fish after that.

Gargantuanalien047, looking forward to Alien Romulus

it's hard to believe that sounds would travel through steel or titanium walls either.