What makes the sound when balloons pop?

[mahela007]

What makes the sound then balloons pop? I don't think it's the air expanding because it's at more or less the same pressure as the atmosphere right? As air is pumped in the balloon expands and therefore he pressures inside and outside are at least roughly equal. I've heard that it's the membrane that causes the sound.. is that right?

 

[redargon]

My guess is that the burst balloon fabric, which was stretched significantly, returns to its initial shape. This probably happens faster than the speed of sound causing shockwaves to form and generating the pressure change that you hear as a pop.

 

[Born2bwire]

The pressure inside the balloon is greater than the normal atmospheric pressure outside of it. You have to apply a force to expand the rubber balloon.

And I'm not sure if it's from the rubber itself. I don't recall the popping of a water balloon to be all that loud. When a balloon filled with air bursts, the outward movement of the compressed air will create a shockwave, probably something similar to an impulse, that could be the *POP* that we hear. Filling the balloon with a more viscuous fluid, like water, would eliminate the contribution from the expanding air and it's my recollection that these are quieter.

 

[redargon]

indeed. A sudden decrease in pressure could cause a shockwave as the compressed air expands to fill it's atmospheric volume. As has ben mentioned by born2bwire, the pressure in the balloon is higher than atmospheric and is a function of the pressure required to expand the balloons fabric. (It works with paper bags too!) I think my previous answer was premature and is incorrect.