Eli5: Why does sound have a set speed if sound is just the air’s movement

Question

Don’t dumb it down too much

In: Physics

Answer 1

Sound actually doesn’t have a set speed. The general speed, 343 m/s is assuming dry air at a temp of 20 C.

So sound waves change speed depending on the density and rigidity(bulk/shear modulus) of the medium they are moving through.

It will have a different speed moving through water, or Jello, or a wall.