The power of sound

We talked yesterday about how a guitar string produces such nice, long notes that are pleasing to the ear - I want to expand on that today.

A visible sound wave in the air - did you know that air can ripple just like water?

Sounds are all caused and detected by vibrations - when you speak, your vocal cords are vibrating in a way that you fine tuned during your early years of life. Starting at 6 months, babies actually watch people's mouths instead of their eyeballs because they're learning how different sounds are formed.

This is just adorable - you can tell that he has no idea what those words are, but he knows the sounds! Also he's 3 years old haha

All sounds are vibrations in a material that vibrates the material next to them - even and especially air. The air carries the sound through a series of vibrations; when they hit your eardrum, it vibrates and your brain decodes those vibrations.

Not quite like this little rascal

Sound's reliance on vibrations is why those waves cannot travel through space: there's no air to vibrate. If you knocked on the outside of a spaceship, they could hear it inside because the metal would vibrate the air inside, but you wouldn't be able to hear it even if you were very close. So every sci-fi movie with pew-pew laser noises or explosions (I'm looking at you, Star Wars), is scientifically inaccurate.

So, for once, a gif has the correct sound it would make

If a moving object (NOT in space) is making a noise, the sound wave produced will be smooshed in the front and elongated in the back; you can replicate this effect by moving your finger through the surface of water.

Sound waves are pretty similar to wave waves :)

This is known as the Doppler Effect, and you can hear it any time a noisy object comes toward you and then passes you by:

 Trains are a common example because they make a lot of noise while they're moving

The Doppler Effect is only the difference in frequency, which determines the pitch of the sound - you'll hear a high pitch if the sound is coming toward you, and a low sound if it's moving away from you. Listen to the train again with this in mind :)