Skip to the content
Peabody TeachFor teachers and grown-ups

A Sound Channel Deep Under the Sea

8th grade nonfiction passage about sound in the deep ocean: 256 words, six questions, an answer key and vocabulary.

8th grade nonfiction sound in the deep ocean 256 words

A Sound Channel Deep Under the Sea

Sound behaves strangely in the deep ocean. Under the right conditions, it can travel for enormous distances, bending along a path as though it were guided through a pipe. This path is known as the deep sound channel, and it exists because of how temperature and pressure change with depth.

Sound moves at different speeds in different parts of the sea. Warm water speeds it up, and so does greater pressure. Near the surface, the water is warm, so sound travels fairly fast. As you go deeper, the water grows colder and sound slows down. Far below, though, the temperature stops falling, while the pressure keeps climbing, and that causes sound to speed up again. Somewhere in between lies a layer where sound travels most slowly.

This matters because sound waves bend toward regions where they travel more slowly, much as light bends when it enters water. A sound that starts in or near the slow layer keeps getting bent back toward it. Instead of spreading out and fading, it stays trapped in a thin band, rising and falling around the slow layer as it moves along. Very little energy is lost to the surface or the sea floor, so the sound can carry far.

Scientists put the channel to use. By sending low-pitched signals across wide stretches of ocean and measuring how long they take to arrive, they can gather clues about the temperature of the water along the way. A hidden layer inside the sea turns out to be a highway for sound.

Questions

  1. What is the deep sound channel? in the text

  2. What makes sound travel faster near the surface? in the text

  3. What makes sound speed up again far below the surface? in the text

  4. Why does sound inside the channel not fade quickly? think about it

  5. Why can travel times of signals tell scientists about water temperature? think about it

  6. Why is the channel compared to a highway? think about it

Words to know

channel
a narrow path that something flows or travels along
pressure
the push of the water above pressing down on what is below
layer
one level lying on top of or beneath others
energy
the power that makes things move or change
signals
messages or sounds sent from one place to another
Share

One passage, three levels

The same topic and facts written three ways, so a mixed class can read and talk about one text. Each group’s sheet shows only a shape; the key says which is which.

● Easier · 241 words · Flesch-Kincaid grade 4.6

Sound acts strangely in the deep ocean. In the right conditions, it can travel very far, bending along a path as if it were guided through a pipe. This path is called the deep sound channel. It exists because of how temperature and pressure change with depth.

Sound moves at different speeds in different parts of the sea. Warm water makes it faster. So does greater pressure. Near the surface, the water is warm, so sound is fairly fast. Deeper down, the water is colder and sound slows. Far below, the temperature stops falling, but the pressure keeps climbing. That makes sound speed up again. Somewhere in the middle is a layer where sound is slowest.

This matters because sound waves bend toward places where they move more slowly, much as light bends when it enters water. A sound that starts in or near the slow layer keeps getting bent back toward it. It does not spread out and fade. It stays trapped in a thin band, rising and falling around the slow layer as it moves along. Very little energy is lost to the surface or the sea floor, so the sound goes far.

Scientists use the channel. They send low-pitched signals across wide stretches of ocean and measure how long the signals take to arrive. This gives clues about the temperature of the water along the way. A hidden layer in the sea is a highway for sound.

▲ This passage · 256 words · Flesch-Kincaid grade 6.8

Sound behaves strangely in the deep ocean. Under the right conditions, it can travel for enormous distances, bending along a path as though it were guided through a pipe. This path is known as the deep sound channel, and it exists because of how temperature and pressure change with depth.

Sound moves at different speeds in different parts of the sea. Warm water speeds it up, and so does greater pressure. Near the surface, the water is warm, so sound travels fairly fast. As you go deeper, the water grows colder and sound slows down. Far below, though, the temperature stops falling, while the pressure keeps climbing, and that causes sound to speed up again. Somewhere in between lies a layer where sound travels most slowly.

This matters because sound waves bend toward regions where they travel more slowly, much as light bends when it enters water. A sound that starts in or near the slow layer keeps getting bent back toward it. Instead of spreading out and fading, it stays trapped in a thin band, rising and falling around the slow layer as it moves along. Very little energy is lost to the surface or the sea floor, so the sound can carry far.

Scientists put the channel to use. By sending low-pitched signals across wide stretches of ocean and measuring how long they take to arrive, they can gather clues about the temperature of the water along the way. A hidden layer inside the sea turns out to be a highway for sound.

■ Harder · 274 words · Flesch-Kincaid grade 8

Sound behaves in a remarkably peculiar manner in the deep ocean. Under the right conditions, it can travel across enormous distances, curving along a path as though it were being guided through a pipe. This path is known as the deep sound channel, and it exists because of the way temperature and pressure change as depth increases.

Sound moves at different speeds in different parts of the sea. Warm water speeds it up, and so does greater pressure. Near the surface, the water is warm, so sound travels fairly quickly. As you descend, the water grows colder and sound slows down. Far below, however, the temperature stops falling while the pressure continues to climb, and that causes sound to speed up again. Somewhere in between lies a layer in which sound travels most slowly of all.

This is significant because sound waves bend toward regions where they travel more slowly, much as light bends when it passes into water. A sound that begins in or near the slow layer is continually bent back toward it. Rather than spreading out and fading away, it remains trapped in a thin band, rising and falling around the slow layer as it moves along. Very little energy is lost to the surface or the sea floor, so the sound is able to carry a great distance.

Scientists have put the channel to use. By sending low-pitched signals across wide stretches of ocean and measuring how long they take to arrive, they can gather clues about the temperature of the water along the way. A hidden layer inside the sea turns out to be a highway for sound.

Download as one PDF

How to use it

  1. Press Read it big (or B) to put the text on the projector, or Full screen (F) to fill the whole screen.
  2. Ask the questions one at a time and use Show answer when the class has decided. A shows or hides every answer.
  3. Print student copy for the class, or Print with answers for yourself.

Ideas for class

  • Before reading, put channel, pressure, layer, energy and signals on the board with their meanings from the Words to know section and have students predict what the text will be about.
  • Read it aloud once while students follow along, then have them reread it alone or with a partner. At a calm 100 words a minute it takes about 3 minutes to read aloud.
  • Use the Read it big button (or B) to put the text on the projector, and Show answer on one question at a time so the class commits to an answer first.
  • Question 4 asks the reader to infer. Ask students to point to the words in the passage that led them to their answer.
  • Ask students to write one question the passage did not answer, then look for the answer in a book or on a classroom screen.
  • Print the student copy for independent work and keep the answer-key copy for yourself.

Related

Questions

What reading level is "A Sound Channel Deep Under the Sea"?

It was written for 8th grade. It has 256 words and works out to a Flesch-Kincaid grade level of about 6.8. That is a formula's estimate from sentence length and syllables, and it is not a Lexile or a guided reading level, so check it against your students.

What do the questions ask?

There are six. 3 ask for something the text says directly and 3 ask the reader to work something out from clues. Each has an answer in the key, and the answers are written as a teacher would accept them, not as the only possible wording.

How long does it take to read?

About 3 minutes read aloud at 100 words a minute. For a one-minute fluency check, paste it into the fluency timer and use the word count.

Can I print it?

Yes. Print student copy gives the passage, the questions with lines to write on, and the word meanings. Print with answers gives the same page with the answers filled in. Both are made in your browser.

Is this passage from a published book?

No. It was written for Peabody Teach, so there is no book to buy and no login to read it.

Nothing you do here is sent to us. No sign-in, no ads.