Can you hear this noise? [beep] Of course you can. It’s well within the hearing frequency range of humans. What about this? Probably not, unless you’re furry and bark when your human won’t take you out. And what if you paddle with two webbed feet and quack? What do ducks hear underwater? That, as it happens, was one of science’s unanswered — actually, unasked — questions until now. Scientists from the University of Delaware have changed that by creating an underwater hearing test for ducks. First, ducklings learn to peck a target like this pipe. Then they hear a sound and receive a treat. After months of work to learn the complicated sequence of the real test, a few of the ducks graduate to the big pool. Here’s how it goes: An LED light tells the duck to dive. We can’t see it. The duck pecks a target — the pipe. If it hears the second sound underwater — [beep] Then it rises to peck the second target and get a treat. By changing the frequency of the second sound, researchers learn the range of duck hearing. Researchers did dozens of experiments — some with one duck, some with more, and tried various frequencies. Here’s one of the researchers, Kate McGrew, monitoring the ducks and controlling the beeps. [click] Some ducks didn’t make the cut. So why does it matter what ducks hear? Diving ducks, also called sea ducks, are getting caught and killed in commercial fishing nets — probably many thousands of them, although the numbers are hard to pin down. Devices that send out sounds or pings have been used to warn dolphins away from nets. So, they might work with ducks. The trick is, the sounds have to be inaudible to fish and audible to ducks. Early indications from the study are that the prime range for duck hearing underwater is between 1 and 3 kilohertz. That’s good to know, but it does present some practical problems because fish hear up to 2 kilohertz, and you don’t want to scare them away. But it’s a great first step in understanding duck hearing.