EAVESDROPS ON ANIMALS ACTIVITY 1: The Right Frequency

Each sound we hear comes to our ears as an invisible wave. Each sound’s wave can come fast and close together, or slow and easy, spread apart. The sounds with close-together waves are the high-pitched sounds, like the way a mouse squeaks or a bird chirps. The sounds that come slow and easy are the low-pitched sounds. When we make low growls or boom like a big drum we are making low-pitched sounds.

We can picture those waves like this:

High frequency (high pitch)

Low frequency (low pitch)

We measure frequency in Hertz (or Hz, for short). Hertz is how many waves fit into one second. High-frequency sounds have a large Hertz, and low-frequency sounds have a low Hertz.

8 STEAM Squad Humans can hear sounds between 20 and 20,000 Hertz. Other animals can speak to each other outside our hearing range. That means all sorts of creatures are having conversations all around us that we can’t hear. Luckily for us, we’ve built transducers that can help us eavesdrop on animals. a tool that sducer is A tran w down p or slo ed u hear them. n spe e can ca so w aves ndw sou

Halloooo! Anybody out there?

STEAM Squad 9 EAVESDROPS ON ANIMALS Look at this chart that shows different animals’ auditory ranges. Think about how they compare to what we can hear.

the range range is itory aud mal can hear. The an ani ounds of s Infrasound (too LOW for humans to hear) Ultrasound Human range (too HIGH for humans to hear)

0 10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000 90,000 100,000

20Hz 20,000Hz Humans 20Hz–20,000Hz

500Hz 38,000Hz Florida manatee 500Hz–38,000Hz

9,000Hz Little brown bat 9,000Hz–200,000Hz

500Hz Killer whale 500Hz–120,000Hz

5Hz 16,000Hz African elephant 5Hz–16,000Hz

AUDITORY RANGE (in Hertz)

10 STEAM Squad mmm h hu um um m h m m Researchers recently u h discovered that giraffes, long thought to be Quiet Quincys, hum happy tunes to each other in infrasound! Ultrasound (too HIGH for humans to hear)

100,000 110,000 120,000 130,000 140,000 150,000 160,000 170,000 180,000 190,000 200,000

Humans 20Hz–20,000Hz

200,000Hz

120,000Hz Killer whale 500Hz–120,000Hz

African elephant 5Hz–16,000Hz ARRR RO !!

White-footed mice are small but mighty. Males sing special songs to their girlfriends, and their girlfriends roar back. It’s all in ultrasound, so we can’t hear it!

STEAM Squad 11 EAVESDROPS ON ANIMALS

I want to design a transducer so we can hear each animal.

Let’s do a little math to find the range for each animal that Eloise needs to transduce.

Help Eloise design her transducer. Use the chart on the previous page to answer these questions.

How many more Hertz can Florida manatees hear than humans can hear? ______answer: 38,000–20,000 = 18,000 Hz

Can manatees hear in our ultrasound or infrasound? (circle one)

What is the range that humans can hear that Florida manatees cannot hear? ______answer: 20Hz–499Hz

How many more Hertz can little brown bats hear than humans? ______

Can little brown bats hear in ultrasound or infrasound? (circle one)

12 STEAM Squad What is the range that humans can hear that little brown bats can’t hear? ______

How many more Hertz can killer whales hear than humans? ______

Can killer whales hear in infrasound or ultrasound? (circle one)

What is the range that humans can hear that killer whales can’t hear? ______

How much lower can elephants hear than humans can? ______

Can elephants hear in infrasound or ultrasound? (circle one)

What is the range that humans can hear that African elephants cannot hear? ______

STEAM Squad 13