[talanum1 (OP)]

The air is always in thermal motion. Then why don't soap bubbles vibrate?

[Colin2B]

The air is always in thermal motion. Then why don't soap bubbles vibrate?

What makes you think they don’t?

[Kryptid]

I imagine the human eye just isn't sensitive enough to see it.

[evan_au]

If you poke a soap bubble to make it vibrate, you will probably break it.

An elastic soap film enclosing compressible air will have a number of vibration modes, so I expect that it will vibrate, if you hit it with sound at the right frequency. But bump up the amplitude too high and you will burst it (or take too long, and it will burst by itself).

A better experimental subject would be a child's rubber balloon. They can be much larger, the resonant frequencies will be lower, and sustain a vibration of larger amplitude.