Skip to the content
Peabody TeachFor teachers and grown-ups

Why a Guitar Needs an Empty Box

8th grade nonfiction passage about resonance and sound boxes: 270 words, six questions, an answer key and vocabulary.

8th grade nonfiction resonance and sound boxes 270 words

Why a Guitar Needs an Empty Box

A guitar string is thin, and by itself it makes hardly any sound that you could hear across a room. Stretch one over a block of wood, pluck it, and you will hear only a faint buzz. Yet the same string on a guitar fills a room with a rich tone. The secret is the hollow wooden body, which works as an amplifier without using any electricity.

Because a vibrating string is so thin, it pushes on very little air, and so it passes its vibrations through a small piece called the bridge, which is glued to the thin top of the guitar. The top begins to vibrate too, and since its surface is much larger than the string, it moves far more air, and a bigger push on the air makes a louder sound.

The empty space inside matters as well, because the air in the box vibrates along with the top, and the sound hole lets that moving air escape into the room. Builders shape and brace the top with great care, because its thickness and stiffness decide which pitches are strengthened and which are not, which is one reason two guitars can sound different even when they wear the same strings.

An amplifier of this kind does not create energy. All of the sound comes from the energy of the plucked string. A loud note on a hollow guitar therefore fades sooner than a quiet note on a solid block, because the string's energy is spent faster when it is sent into the air. The hollow body trades a long, quiet note for a short, loud one.

Questions

  1. Why does a guitar string alone make so little sound? in the text

  2. What small part passes the string's vibrations to the top of the guitar? in the text

  3. What does the sound hole let escape into the room? in the text

  4. Why does the large top make a louder sound than the string does? in the text

  5. Why can two guitars with the same strings sound different? think about it

  6. Why does a loud note on a hollow guitar fade sooner than a quiet one on solid wood? think about it

Words to know

vibrate
to move back and forth very quickly
amplifier
something that makes a sound louder
bridge
the small piece that holds the strings up and carries their shaking
pitches
how high or low sounds are
stiffness
how hard something is to bend
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 · 201 words · Flesch-Kincaid grade 2

A guitar string is thin. By itself, it makes almost no sound. Put one on a block of wood and pluck it. You will hear only a faint buzz. But on a guitar, the same string sounds rich and loud. The hollow body of the guitar is the secret.

A thin string pushes on very little air. So the string passes its shaking to a small piece called the bridge. The bridge is glued to the thin top of the guitar. The top starts to shake too. The top is much bigger than the string. It moves a lot more air. More moving air makes a louder sound.

The empty space inside helps as well. The air in the box shakes with the top. The sound hole lets that air out into the room. Builders shape the top with care. Its thickness and stiffness change which pitches get stronger. That is why two guitars can sound different with the same strings.

The guitar does not make new energy. The sound comes from the plucked string. A loud note fades sooner than a quiet one on solid wood. The string uses up its energy faster when it sends sound into the air.

▲ This passage · 270 words · Flesch-Kincaid grade 8.4

A guitar string is thin, and by itself it makes hardly any sound that you could hear across a room. Stretch one over a block of wood, pluck it, and you will hear only a faint buzz. Yet the same string on a guitar fills a room with a rich tone. The secret is the hollow wooden body, which works as an amplifier without using any electricity.

Because a vibrating string is so thin, it pushes on very little air, and so it passes its vibrations through a small piece called the bridge, which is glued to the thin top of the guitar. The top begins to vibrate too, and since its surface is much larger than the string, it moves far more air, and a bigger push on the air makes a louder sound.

The empty space inside matters as well, because the air in the box vibrates along with the top, and the sound hole lets that moving air escape into the room. Builders shape and brace the top with great care, because its thickness and stiffness decide which pitches are strengthened and which are not, which is one reason two guitars can sound different even when they wear the same strings.

An amplifier of this kind does not create energy. All of the sound comes from the energy of the plucked string. A loud note on a hollow guitar therefore fades sooner than a quiet note on a solid block, because the string's energy is spent faster when it is sent into the air. The hollow body trades a long, quiet note for a short, loud one.

■ Harder · 310 words · Flesch-Kincaid grade 9.6

On its own, a guitar string is so slender that it produces hardly any sound a listener could detect from across a room. Stretch the same string over a plain block of wood, pluck it, and the result is only a faint buzz. Mounted on a guitar, however, that very string fills an entire room with a warm, rich tone. The explanation is the hollow wooden body, which serves as an amplifier without drawing any electricity at all.

Because a vibrating string is so thin, it disturbs only a tiny amount of air. Instead, the string delivers its vibrations through a small piece known as the bridge, which is glued to the thin top of the instrument. The top begins to vibrate as well, and since its surface is far larger than the string, it sets a much greater volume of air in motion. A bigger push on the air produces a louder sound.

The empty space inside the body contributes too. The air enclosed in the box vibrates together with the top, and the sound hole allows that moving air to escape into the surrounding room. Builders shape and brace the top with great care, since its thickness and stiffness determine which pitches are strengthened and which are left weak. This is one reason why two guitars can sound distinctly different, even when they carry identical strings and are plucked in precisely the same manner.

An amplifier of this kind never creates energy, since every bit of the sound comes from the energy of the plucked string, and consequently a loud note on a hollow guitar dies away sooner than a quiet note on a solid block, because the string's energy is used up more quickly when it is sent out into the air. The hollow body, in effect, exchanges a long, quiet note for a short, loud one.

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 vibrate, amplifier, bridge, pitches and stiffness 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 5 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 "Why a Guitar Needs an Empty Box"?

It was written for 8th grade. It has 270 words and works out to a Flesch-Kincaid grade level of about 8.4. 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. 4 ask for something the text says directly and 2 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.