Follow your curiosity

What discovery has been shared with you?

FACTREE gives you something interesting to discover every day — and something worth talking about together.

Start with one fact. Explore it, go deeper, then follow whichever branch catches your imagination.

Choose subjects for a surprise

Exploring any topic

Begin your discovery

Your next discovery is one click away.

Choose one or more subjects above, or leave Any Topic selected and let curiosity decide.

Physics

Acoustic Impedance

Quick fact

At a boundary between air and water, only about 0.1% of sound energy is transmitted; the rest is reflected back. This is why underwater sounds are nearly silent to someone above the surface.

Why this is interesting

Why can you hear a whale from miles away underwater, but a loud concert outside feels muffled when you plunge into a pool? The answer lies in a hidden property of every material: its acoustic impedance.