Thanks to Linode Cloud Computing for supporting this episode of SciShow.

Head to linode.com/scishow to learn more and get a $100 60-day credit on a new Linode account. [♪ INTRO] Over the past however many millennia, we have used clothing to protect us against the elements, show off our personal fashion, and argue whether or not washing machines are actually portals to another dimension. Or possibly my socks are just hiding somewhere, plotting revenge against me.

I don’t know. But it turns out our clothes may do even more in the future. This week in the journal Nature, scientists report they have developed a fabric that can hear.

When it comes down to it, sounds are basically just pressure waves. They are a compression and expansion of some kind of medium, like air, happening over and over again as the wave travels through it. In the human body, these pressure waves are translated into physical vibrations that go from one part of the ear to another, moving inward, to a fluid-filled, snail-shaped region called the cochlea.

Living amongst that fluid are teeny tiny hair cells. And when vibrations inside the fluid make the hairs move, they push up against the part of the cochlea’s inner structure and bend a little bit. That bending opens up a channel that lets in a flood of chemicals and creates an electrical signal that travels up your nervous system and into your brain.

And you hear a sound! That’s really how it works. Thanks to advancements in technology, humans have figured out ways to detect and even record sounds without the human ear, from hearing aids to the microphone that is recording my voice right now.

And now, one team is looking to find a way to do it with fabric. Of course, one of the big challenges is that fabrics are often used to dampen sounds, which is kind of the opposite thing you want to have happen when you’re developing a fabric-based microphone. So this team looked to another part of the human ear for guidance.

The tympanic membrane, colloquially known as the eardrum. It is made out of four layers of collagen fibers, carefully arranged so that some of them point directly out from the center, and others arc around at right angles. So this team’s fabric mimics that same setup, but instead of collagen, they use two different kinds of yarn.

One is a simple cotton, and the other is a synthetic name brand called Twaron. Inside that, they wove a single fiber made out of a special material that’s piezoelectric, which means that it can translate mechanical vibration into electricity. In other words, that fiber will do the job of our cochleas.

So when the sound wave deforms the fabric it creates an electrical charge which, if connected to a circuit, allows electricity to flow. The team tested their fabric-based microphone on a few sounds, from rustling leaves to someone clapping. And it turns out that the quietest sounds it picked up were equivalent to what you would find in a library.

And when two separate patches of fabric were tested on a single shirt, they were able to figure out where a sound originated, if it was within a certain range. But wait, there’s more! Because if you want to make clothing that can hear for you, it’s got to be able to be, you know, worn.

So, in addition to testing how their piezoelectric fiber held up to deformation, like what would happen if you were moving around in a t-shirt made of the stuff, they also threw it in the wash. Ten times. And it worked basically just as well.

The team highlighted a few applications for this fabric, like helping people who are hard of hearing, or even monitoring the wearer’s health by acting like a big wraparound stethoscope. I, for one, plan on using it as a secret agent for my new work with the association of missing socks… or maybe as some kind of tool for understanding my pets better…I’m just trying to make a transition to the next story. As much as we would like to pretend to have conversations with our pets, or even the random squirrel that crosses our path, it can be difficult to interpret the sounds animals use to communicate their feelings.

If you would like to have that superpower, well, we might be one step closer to deciphering the language of pigs, as a team reported last week in the journal Scientific Reports. Over the past decade, research has been able to demonstrate connections between certain vocalizations and certain emotional states, like being under stress. That includes the domesticated pig, which some people keep as pets, while others… love the smell of bacon in the morning.

But in either scenario, it's worth knowing if an animal is stressed. Pigs are known to have pretty complex vocalizations. And past research has shown that high-pitched calls, like squeals, are often produced in negative situations, while low-pitched calls, like grunts, are found in more positive ones.

But in each of those calls, there are a lot of things that can vary, like how long they last, and the amount of oomph the pig puts into it. One international team wanted to figure out how positive and negative emotions could be tracked by more than just pitch. So they tracked the grunts and squeals of over 400 little piggies across Europe, from the moment they were born until the moment they…went to the market.

Altogether, they had over 7,400 calls to study, and they measured several vocal parameters, including duration, amplitude, and my personal favorite, mean Wiener Entropy… …which is a measure of, and I don’t understand what this means, how flat a sound’s intensity registers across a range of frequencies. Anyway, their analysis found that for both high and low-frequency calls, shorter sounds were more positive and longer sounds more negative. That actually matches results from previous research.

The amplitude also varied less in happier situations. But positive low-frequency sounds were more tonal, while positive high-frequency sounds sounded like they had more noise to them, more similar to white noise. And that result actually conflicts with past research.

The team also tried to see if they could train a computer program to classify new pig calls into positive and negative, and one program worked over 90% of the time. So in time, a more sophisticated program could get turned into something like an app that farmers could use to monitor their herds. Of course, all of this relies on scientists assuming that the pigs are actually feeling positive or negative emotions in certain situations.

And they assume that certain emotions are definitely positive or negative. Still, this research is important if we want to help keep animals healthy, not just physically, but mentally. Whether or not we eat them in the end.

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Thanks for watching this episode of SciShow, and thank you to Linode for sponsoring this video. [♪ OUTRO]