If sound travels faster through a solid why can't you hear through solids?

Answer 1

In fact, sound does travel faster in solids than in liquids, and faster in liquids than in air. Also, we canhear through solids, but not very well. And it doesn't have anything to do with the speed of sound in the material. Let's look at what's going on.

If sound originates in air on the other side of a wall, the sound must impinge on the wall to be transmitted through it. Some of the energy is reflected and some is absorbed, so that doesn't leave much to come through to where we might be listening. Also, you can hear better with an ear to the wall. But if the sound originates in the solid wall, you can hear it better, and can hear it very well with an ear pressed to the wall. This is because the solid will propagate it better (as well as faster) than it would travel in a liquid or in air.

You might recall the old Indian trick of putting an ear to the rails to listen to find out if a train was coming. The sound is conducted in the solid rails (even with the spacing between sections) better than through the air. These people didn't know why this was so, but they knew that it was a fact.