Science & Technology

What Does Cold Sound Like? See If Your Ear Can Tell Temperature

By NPR Staff

Published July 5, 2014 at 2:30 PM CDT

Can you hear the difference between hot and cold?

A British "sensory branding company" called Condiment Junkie wanted to know the answer. They specialize in sound design for all sorts of advertisements. Now they're taking a look at how they might use sound design to make better beverage ads. Take the sound of water pouring in this Twinings Tea commercial.

The marketers wanted to know: Would it be possible to make that noise itself more appealing? Can people hear the difference between a hot cup of tea being poured and, say, a cold beer? And is it possible to make a hot drink sound hotter or a cold drink sound more refreshing?

So they did an experiment. They played sounds of hot and cold water being poured into glasses and asked people to guess: hot or cold? The results were kind of insane. Ninety-six percent of people can tell the difference between hot and cold, just by the sound.

So, can you hear the difference?

Glass 1

Glass 2

Glass 1,as 80 percent of you were able to tell, was cold.

Glass 2,as more than 90 percent of you detected, was hot.

Condiment Junkie, the sensory branding company behind these sounds, is trying to isolate exactly what it is about the sound of hot or cold water that tips people off to its temperature. And the answer isn't the difference between cups and mugs, as some commenters guessed — Glass 1 and Glass 2 were identical containers.

Scientists have long known that cold water is more viscous than hot water, because the molecules are wiggling less rapidly, so they are effectively stickier. How viscous a liquid is affects how it pours, and therefore how it sounds. Scott King, one of the founders of Condiment Junkie, says bubbliness is also a factor.

"There tends to be more bubbling in a liquid that's hot," he explains. "As you have more bubbling, you tend to get higher frequency sounds from it."

You can hear that effect in the sound of Glass 2, above. It begins and ends with a high-pitched ringing sound. The question for Condiment Junkie is whether it's possible to make liquid sound hotter or colder by, for example, accentuating that ringing.