Why does sound echo in empty rooms?

Answer: Hard surfaces reflect sound waves

Hard surfaces reflect sound waves ✓ — Correct! Echoes are reflected sound waves. In empty rooms, hard surfaces (walls, floors, ceilings) have nothing to absorb sound energy, so waves reflect back and forth multiple times before dissipating. Furniture, curtains, and carpet absorb sound energy, reducing reflections. This is why empty rooms sound 'hollow'—you're hearing multiple reflections of your voice.

Silence amplifies all sounds — Wrong. Silence doesn't amplify sounds. Empty rooms sound louder because hard surfaces reflect sound instead of absorbing it, so more sound energy reaches your ears through multiple reflections (echoes). It's not amplification—it's lack of absorption. The total sound energy is the same, but more of it bounces back to you instead of being absorbed by furniture and materials.

Air molecules bounce around more — Wrong. Air molecules behave the same in empty versus furnished rooms. Echoes occur because sound waves reflect off hard surfaces. In furnished rooms, soft materials (fabric, foam, wood) absorb sound energy, preventing reflections. In empty rooms, hard surfaces reflect sound waves repeatedly, creating echoes. It's about surface properties, not air molecule behavior.