What if you could hear like a bat?

On a summer evening, bats fly over the garden. They swoop and turn.

They are calling out, but you can't hear them! What if you could hear like a bat?

On a warm evening, you might see bats darting through the sky above a pond or a streetlight, twisting and turning to catch insects. They're making lots of noise as they fly, but you can't hear a thing.

That's because bats call in sounds too high for human ears. So what if you could hear like a bat? What would the night sound like, and could you use echoes to find your way? Let's follow the clues.

Every ear has a frequency range it can detect. Humans hear a wide band, but many animals hear sounds outside it, both higher and lower. Bats live much of their lives in sound we cannot perceive.

This thought experiment extends human hearing to a bat's range and asks what would change. It follows three threads: what very high sounds are, how bats use them to echolocate, and how different animals' hearing ranges compare. Measured values come from physics and natural history sources; the human experience of bat hearing is an idea.

Sounds are made by things shaking back and forth very fast. That is called vibrating.

You can hear low sounds like a drum and high sounds like a whistle. But some sounds are too high for you!

Sound reaches your ears as vibrations. How many vibrations happen each second is called the frequency, measured in hertz (Hz). Your brain hears frequency as pitch, how high or low a note sounds.

The OpenStax physics textbook says normal human hearing covers about 20 to 20,000 hertz. That's an impressive range, but there are sounds beyond it. Sounds below 20 hertz are called infrasound, and sounds above 20,000 hertz are called ultrasound. We can't hear either one, although very low sounds can sometimes be felt as vibrations.

OpenStax defines hearing as the perception of sound and gives normal human hearing as 20 to 20,000 Hz. Sound below 20 Hz is infrasound and above 20,000 Hz is ultrasound; neither is perceived by the ear, though infrasound can sometimes be felt as vibration.

OpenStax defines pitch as the perception of frequency, directly related to it; people can typically tell apart two tones whose frequencies differ by 0.3 percent, such as 500.0 and 501.5 Hz. Other animals' ranges differ: OpenStax notes that dogs can hear up to 30,000 Hz, bats and dolphins up to 100,000 Hz, and elephants respond to frequencies below 20 Hz.

Now pretend you have bat ears. You can hear super high sounds!

At night, you might hear bats calling as they fly by. Chirp, chirp, chirp!

With bat ears, you could hear sounds up to about 100,000 hertz, five times higher than you can now. A summer evening might suddenly sound busy: the National Park Service says bats call out while they hunt, and each kind of bat has its own call pattern.

You might also hear a dog whistle, which makes a sound too high for people but not for dogs. Whether all those extra sounds would be fun or just noisy is an idea we can only guess about.

Extending the upper limit from 20 kHz to about 100 kHz would bring bat calls into hearing. The little brown bat's calls, sweeping from about 80 to 40 kHz, lie entirely above human hearing; cruising bats produce about 20 calls per second (Animal Diversity Web). Dog whistles, which OpenStax notes are outside human range, would become audible too.

How a human brain would interpret this new band is unknowable here: perceiving sound is not only about the ear's range, and using echoes takes more than hearing them. Those consequences stay ideas.

A bat shouts a high sound. The sound bounces off a bug and comes back.

The bat listens to the echo. Now it knows where the bug is!

Bats use echolocation to find their way and catch insects. A bat sends out a high-pitched call, the sound bounces off objects around it, and the echoes return to the bat's ears. The National Park Service says bat ears are finely tuned to recognize their own calls.

When a bat finds an insect, it speeds up its calls into a rapid series, called a feeding buzz, to pin down exactly where the insect is. Then it swoops in and catches its dinner.

The National Park Service describes echolocation: bats emit ultrasound, which reflects from objects; the returning echoes reach ears finely tuned to recognize the bat's own unique calls. When a bat detects prey, it produces a rapid series of calls, a 'feeding buzz,' to pinpoint its location before capture.

Animal Diversity Web records that the little brown bat (Myotis lucifugus) uses frequency-modulated calls lasting 1 to 5 milliseconds, sweeping downward from about 80 to 40 kHz with a fundamental near 45 kHz. Bats change their calls for searching, feeding and social purposes.

Scientists have special microphones that catch bat calls.

They slow the sounds down so people can hear them!

We can't hear bats, but scientists can. The National Park Service explains that scientists record bat calls with special microphones and turn them into sounds people can hear and pictures they can see, called spectrograms. One trick is to slow a recording down ten times, which lowers the pitch into our hearing range.

Each kind of bat has its own call pattern, so scientists can tell which bats live in a park just by listening. And one bat, the spotted bat, calls low enough that people with good hearing can faintly hear it.

Researchers identify and study bats by recording their calls with specialized microphones and translating them into audible sound and spectrograms (National Park Service). Slowing recordings ten times divides every frequency by ten, bringing a 45 kHz call down to 4.5 kHz, well within human hearing; that arithmetic is ours.

Because each species has its own call pattern, acoustic surveys can identify bats without catching them. The spotted bat (Euderma maculatum) is an exception to inaudibility: the Park Service notes that its echolocation call is faintly audible to people with good hearing.