We are able to hear easily through the walls of many rooms because the material used in those walls are good conductors of sound. We know that some things are better conductors of heat than others, and just in that same way, some things conduct sound better than others. Wood has been shown to be an even better conductor of sound than air. Most of us have stood at the foot of an overhead trolley pole to see if we could hear a car coming, and we know that the reason we did this was because we could hear the wire humming, when we put our ears against the pole, even though we could not hear any sound in the air.

When we are in a room that has wooden walls we can hear sounds in the next room very plainly, not because the wall is thin, but because the wood in the wall is a good conductor of sound. Other walls made of different kinds of material, are not as good conductors of sound. While you may hear through them, you cannot hear as plainly as you can through a wooden wall.