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TEACHING GUIDES


INVENTING THE FUTURE TEACHING GUIDE:
Brain Music


Blending opera and computer technology, the Brain Opera is a unique, interactive musical event created by composer Tod Machover and a team of artists and scientists at the MIT Media Lab. A synthesis of art, music and technology, the opera invites the audience to make music on hyperinstruments, which is incorporated into the performance. MIT musician-scientists performed the opera at the Lincoln Center Festival in New York City during the summer of 1996; it is currently on international tour.

Curriculum Links
Activity 1: Bottled Sounds
Activity 2: Straw Pipes
For Further Thought


CURRICULUM LINKS

COMPUTER SCIENCE

artificial intelligence

MATH

ratios

MUSIC

composition and theory

PHYSICAL SCIENCE/PHYSICS

acoustics
pitch
sound waves

PSYCHOLOGY

brain

TECHNOLOGY

inventions


ACTIVITY 1: BOTTLED SOUNDS

As you see on Frontiers, the Brain Opera uses high-tech hyperinstruments to create musical compositions. But low-tech instruments like the glass harmonica can also be used to make music. The sounds produced with these homemade instruments can be used to find out more about sound and pitch. The Bottled Sounds extension is a simplified version of Ben Franklin's glass harmonica, an instrument using a series of graduated glasses or glass bowls that produce different tones when the edges are rubbed with a wet finger.

MATERIALS

  • 5 identical glass beverage bottles
  • water
  • metal spoon

OBJECTIVE

In these activities, students will operationally define the relationship between the length of a vibrating air column and the pitch of the sound produced.

PROCEDURE

  • 1.Work with a partner. Fill one bottle to the top with water. Fill the second bottle 3/4 full, the third bottle 1/2 full and the fourth 1/4 full. Leave the fifth bottle empty.
  • 2. Gently strike the side of each bottle with a metal spoon. Observe the pitch of each note.
  • 3. Adjust the amount of water in each bottle to make notes in a recognizable musical phrase, such as "Happy Birthday to You."
  • 4. Now blow across the top of each bottle. Observe the pitch of each bottle's note.

QUESTIONS

  • 1. How does the pitch of the bottle relate to the level of water when the bottle is struck by a spoon?
  • 2. How does the pitch relate to the level of water when air is blown across the top of the bottle?
  • 3. Compare and contrast the two sound-making techniques. What material vibrates to produce the note when the bottle is struck? What material vibrates when air is blown across the top?
  • 4. Would changing the size of the spoon affect the pitch? How?
  • 5. Does the height of the strike affect the pitch? Explain.

ANSWERS

  • 1. More water, lower pitch.
  • 2. More water, higher pitch.
  • 3. The water within the bottle; the air within the bottle.
  • 4. No. It would change the amount of energy added to the system. Although the pitch would remain the same, the loudness would vary with the size of the striking mallet.
  • 5. No. It doesn't matter where the strike occurs. The energy of impact is transferred through the glass to the liquid.

EXTENSION

Fill a glass halfway with water. Wet your finger by dipping it into the water. Slowly circle the moist finger around the rim of the glass. Keep moving your finger at a steady rate. Make sure your finger remains moist. When the friction between the moving finger and the glass rim is correct, the glass will begin to "sing." Try building a complete octave by assembling a set of glasses with different amounts of water. Try doing the experiment with different kinds of glasses.

ACTIVITY 2: STRAW PIPES

The linear body of a wind instrument, like a flute, contains a column of air. When this air is set in motion, it vibrates. These vibrations travel outward and reach our ears as notes of a scale.

The pitch of the notes depends upon the length of the vibrating air column. If the column stretches along the entire length of the flute, its note is low. When the instrument's holes open, the column is shortened. The air now vibrates from the mouthpiece to the open hole; the pitch becomes shrill.

Most of us are familiar with a basic (diatonic) scale: do - re - mi - fa - sol - la - ti - do. The difference in pitch between the same two notes from one scale to another is called an octave. The notes within an octave have a mathematical arrangement as shown on this table:

  • PITCH: C -- LENGTH RATIO: 1
  • PITCH: D -- LENGTH RATIO: 8/9
  • PITCH: E -- LENGTH RATIO: 4/5
  • PITCH: F -- LENGTH RATIO: 3/4
  • PITCH: G -- LENGTH RATIO: 2/3
  • PITCH: A -- LENGTH RATIO: 3/5
  • PITCH: B -- LENGTH RATIO: 8/15
  • PITCH: C -- LENGTH RATIO: 1/2

If, for example, a length of tube 30 cm long produced a low C, then a tube half its length (15 cm) would produce a C one octave higher. A tube 4/5 of the length (20 cm) would produce an E. In the following activity, you'll construct a set of air columns to produce the eight notes of an octave. (Note: the notes of this scale are arbitrary and are not intended to match true notes.)

MATERIALS

  • 8 identical plastic straws per group
  • permanent markers
  • rulers
  • scissors

PROCEDURE

  • 1. Work with a partner. Each of you will construct four of the eight straw instruments.
  • 2. Measure the length of one straw. Record the length as the low "C" note in the chart below (the top box represents the low "C"). Use the ratios shown above to determine the length of straw needed to produce each of the eight notes. Record values in the table below.

  • PITCH: C -- STRAW LENGTH: ___ cm
  • PITCH: D -- STRAW LENGTH: ___ cm
  • PITCH: E -- STRAW LENGTH: ___ cm
  • PITCH: F -- STRAW LENGTH: ___ cm
  • PITCH: G -- STRAW LENGTH: ___ cm
  • PITCH: A -- STRAW LENGTH: ___ cm
  • PITCH: B -- STRAW LENGTH: ___ cm
  • PITCH: C -- STRAW LENGTH: ___ cm

  • 3. Mark the lengths on the eight straws so that you and your partner will have a complete set of eight notes. Trim each straw with scissors to the exact length. You may want to write the name of the note on each straw that you cut.
  • 4. Flatten one end of each straw. Use scissors to cut a small triangular piece off each of the two corners of the flattened end of the straw. The cuts should produce reed-like mouthpieces on all eight straws.
  • 5. Chew down on the mouthpiece end of your straw to flatten it (do not exchange straws with your partner). If chewing or cutting has closed the trimmed end, open it.
  • 6. Place this trimmed end in your mouth and blow lightly. The end should be far enough in your mouth that the flaps are free to vibrate. As you blow, the reed flaps will vibrate, producing a buzzing note. Compare the pitches of the notes produced by straws of different lengths.
  • (Note: If a straw doesn't produce a sound, chew the trimmed end to soften the reed flaps.)

EXTENSIONS

  • Design and build an instrument that produces all eight notes in an octave, using only a single straw.
  • Work with your partner to find out which notes sound pleasant (harmonious) when played together using different straws. Record those note combinations. Also, record the note combinations that do not sound pleasant (discordant).
  • Work with the entire class to produce a "musical story" or opera of pipes with your instruments. The story should include unison notes, harmonious note combinations and discordant note combinations.

CREDIT:

These activities were contributed by Massachusetts science writer Michael DiSpezio, author of Critical Thinking Puzzles (Sterling, 1996).


FOR FURTHER THOUGHT

Do you remember the last time you filled a jug or bottle with water? If so, did the sound produced by the water rising in the jar get lower or higher in pitch? Think about it. Then, from what you've learned, explain your observation.








 

Scientific American Frontiers
Fall 1990 to Spring 2000
Sponsored by GTE Corporation,
now a part of Verizon Communications Inc.