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Whelmer #11: Straw Oboes
 Description:
Reed-like instruments are created from plastic drinking straws.
Science process skills:
observation, measuring and identifying variables
Complex reasoning strategies:
comparison, deduction, supporting, problem solving and composing
Standards:
K-4
- Employ simple equipment and tools to gather data and extend the senses.
(A.1.3)
- Use data to construct reasonable explanations. (A.1.4)
- Sound is produced by vibrating objects. The pitch of the sound can
be varied by changing the rate of vibration. (B.2.4)
5-8
- Energy is a property of many substances and is associated with sound.
(B.3.1)
9-12
- Waves, including sound, have energy and can transfer energy when they
interact with matter. (B.6.1)
From the National
Science Education Standards
Content topics:
production of sound waves, relationship between wavelength, frequency, and
pitch
You will need:
- plastic or paper drinking straws (paper straws work better, if you
can find them)
- scissors
- overhead projector (optional)
Instructions:
This activity takes some practice to master. You should become proficient
at playing a straw oboe before presenting this activity to your students.
Flatten one end (about 2 cm) of a drinking straw. Use your teeth or pinch
it between your fingers. Use scissors to make angular cuts as shown, on
each side of the flattened end.
Insert the straw into your mouth. Position the reed flaps just inside your
lips and apply very light pressure with your lips. Blow through the straw.
The reeds should vibrate and produce a tone. You may need to move the straw
around slightly to locate the best position for creating your musical note.
You can cut portions off the non-flattened end of the straw to create different
pitched tones.
Presentation:
If you elect to use this as a class activity, you can demonstrate each step
of the fabrication process with an overhead projector. Place an example
of each of the three stages on the projector surface: regular straw, flattened
end, and trimmed reeds.
Ask students to explain how the sound is being produced. (vibrating reeds
cause surrounding air to vibrate) You can play a "do-re-me-..."
scale by cutting 1 cm sections off the end of the straw as you are blowing
through it. Be careful. Do not cut you nose with the scissors.
You should ask students where they have seen or experienced similar phenomena.
(other musical instruments, wind blowing through wires and windows, etc.)
Content:
Blowing through the reeds causes them to vibrate. It also causes the column
of air in the straw to vibrate, producing the pitch characteristic to that
length. Cutting the straw shortens the length of the vibrating column of
air, creating a shorter wavelength and higher frequency (pitch) vibration.
High pitched sounds characteristically have shorter wavelengths. Their frequency
of vibration is higher. Frequency is measured in cycles per second or hertz.
5 hertz = 5 cycles per second. 5 kilohertz (5 KHz) = 5000 cycles per second.
Low pitched sounds have longer wavelengths and lower frequencies. Piano
tuners will tune the middle A to 440, meaning 440 hertz. The range for normal
human hearing is from 15 cycles per second on the low end of the scale to
15,000 cycles per second at the high end. The reeds of most straw oboes
vibrate between 200 and 600 cycles second.
Assessment:
Type: small group
Content/Process: production of sound waves
Age/Level: all
In groups, allow the students to experiment with the straws to make different
tones. Have the reeds and mouthpieces of several reed instruments available
along with tubes of varying lengths and tape. Students can use this equipment
and/or the straws to make instruments. They should end with instruments
that can produce sounds that they have predetermined they need to play a
familiar song or piece of music. Students are assessed based on the success
of their efforts.
Students in middle school or above can be challenged to cut the straw to
produce a scale. They should measure and record the straw length for each
note. Have them identify two lengths of straw that produce an octave. They
can match the pitch of the lower straw note to that of a piano note and
measure the length of the corresponding piano string. Have them predict
the length of the piano string that will match the pitch of their higher
straw note and report orally or in writing on their discovery.
Notes:
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