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

The air will be heated slightly by the sound, but not much. The speaker vibrations are giving energy to the air molecules, which are colliding with other air molecules. So the average kinetic energy (thermal energy) per molecule increases slightly.

By ‘thermal energy’, i mean average kinetic energy of molecules. The heat is related to the speed at which the molecules are moving on average.