If soundwaves are compression waves in air molecules, and thermal energy is vibrations in air molecules, why aren’t loud things hot?

Question

Like if I have a really bright flashlight I can feel heat from the beam, but I can blast a speaker at max volume and I might even feel the vibrations in my hand, but there’s no change in temperature.

Is this a glitch in the matrix?

In: Physics

Answer 1

Edit: I misread your question. But I’ll keep my answer below, for why “hot things create sound”…my apologies!

You need a constantly changing temperature to create sound by rapidly changing the density of air in the immediate vicinity, but it is very well possible!

Check out [this carbon nanotube speaker ](https://youtu.be/EA2exNkoq8A), which is essentially just a thin sheet of carbon ntubes changing temperature so rapidly that it is creating sound (and literal music)! There is no moving components here, it is just the black sheet that is playing music.