Question

If a soundproof door is almost shut but still leaves a small opening, what wave phenomenon is responsible for someone being able to hear sound from the room while standing by the wall to the side of the opening?

absorption
diffraction
reflection
refraction

Answer 1

Diffraction.

Sound waves bend and spread out when they pass through a small gap or around an edge. Because audible wavelengths are often comparable to or larger than the tiny opening, the sound diffracts into the area beside the door so you can hear it.