Why Does Ice Make That Crackling Sound When You Pour Liquid Over It?

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You know that crackling, fizzing sound ice makes when you pour liquid over it? Soft drink companies are particularly fond of recreating it in their commercials, like this one:

That oddly satisfying sound is caused by something called differential expansion. Typically, the drink in which you are putting ice is warmer than the cubes (hence the need for ice). When you drop the cold ice into the warm drink, this causes the outer layer of ice to warm up and expand, while the inner layer stays cold and doesn't expand. Periodic Videos describes it as a "tug of war" between the two layers, which results in the cracking sound.

If you let ice cubes warm up on a tray or in a bucket before dropping them into your drink, you probably won't experience the same pops and cracks.

This aural occurrence is not just limited to your soda pop. Glaciers do something similar as they melt, but on a much larger scale:

The noise is called bergy seltzer (sometimes spelled "bergie seltzer"), and it’s produced when air bubbles buried deep in glaciers pop when the ice melts and cracks. And unlike your ice-filled soda, there’s a little bit of history released with every Bergy Seltzer crackle. The air bubbles were captured in the glaciers when the ice first formed, and when they pop, they release air that can be thousands of years old.