When you press you ear against a hollow-core door, how come the sound can be loud enough to hurt your ears?

Question

Even though the room behind is not loud at all when you open it?

How can resonant chambers make things louder, at the same distance from the source, without violating the conservation of energy.

Answer 1

Because you're a wuss.

On a more serious note, it may act as a resonance chamber for given frequencies if n(lamda) = width of the door.

To answer your second point, it also is acting as a wave guide, collecting all of the radiating sound on one side of the door but making it preferentially travel through it (not left or right, say). This also would cause the sound to decay slower over this short interval, but this effect here is negligible.

Answer 2

sounds actually travel better through solid materials... so when you put your ear up to the hollow door, you may actually be hearing sounds that are resonating all over the. also while the door is hollow, it may be creating resonance inside the door and almost amplifying the more faint sounds coming in.