You are trying to sleep in a noisy environment and decide to use a pillow to block out some of the noise. Why might the pillow be effective at reducing sound?

Answer: B. It has air spaces that trap sound waves.

Absorption: Pillows are made of soft, "fluffy" materials like cotton, foam, or feathers. These materials are full of tiny air pockets. When sound waves hit the pillow, they get trapped inside these pockets and bounce around until their energy turns into a tiny amount of heat. This "soaks up" the sound rather than letting it reach your ears.
Damping: Soft surfaces don't vibrate well. Instead of passing the vibration through to your head, the pillow cushions the sound energy and muffles it.

Answering after opening this box earns no Practice Points.