CURWOOD: Coming up: turtles eat it, sea birds eat it…even tiny shrimp eat it. Plastic is finding its way into every part of the marine food chain. But first this Note on Emerging Science from Amy Fish. And you’re listening to Living on Earth.

FISH: Listen up! This could be the sound of a new renewable energy source—cheap, portable, and fueled only by waste heat.

Scientists at the University of Utah start by turning the disorderly energy of heat into a pure, single-frequency sound, using a tube-shaped resonator small enough to fit in the palm of your hand. The resonator contains a stack of plates or fibers. When the tube is heated at one end, the expanding air inside diffuses toward the cold air at the other end. The movement of the air through the stack causes vibrations, which in turn produce a sound wave.

Some versions of the resonators produce 135 decibels. That’s the noise level of a jackhammer. But don’t worry about the racket—researchers promise any sound can easily be muffled.

Once they’ve produced the sound, the Utah scientists use a long-understood phenomenon called the piezoelectric effect to turn the sound waves into electricity. Each cubic centimeter of tube produces about one watt of power.

The devices are small, durable, and cheap to produce, so they might make good portable electricity sources for outfits like the U.S. Army, which is funding the research. And scientists say they could power the process with just about any heat source, from power plant waste heat to a running computer—even the heat of sun.

So—it looks like a little hot air might be useful after all.