Episode Description
Cheston has been invited to play guitar in a recording studio with members of his favorite band. Jessica goes along to see what a recording session is like. Together they discover that different instruments create different sound waves, technology can manipulate those waves, and the music they love is a product of physics!
Curriculum Areas: Science/Math/Music

Concepts/Vocabulary
Acoustics - the study of sound, not limited just to audible sounds (infra sound and ultrasonic sound) where the name "SOUND," or acoustic waves, is now used to describe any wave that has a mechanical support.

Reflection - a property of waves, when encountering a barrier, boundary, or change in medium, to "bounce back," traveling away from the boundary.

Absorption - when a sound wave (or any wave) encounters a barrier or different medium, some of its energy is lost to that medium.

Resonance - vibration of large amplitudes in mechanical systems caused by a relatively small stimulus of nearly the same natural frequency of the system affected (i.e. radio tuner, Tacoma Narrows Bridge).

The Sound Board transfers waves to electrical energy. Music is transformed to electric impulses that travel through cords to the soundboard. The soundboard takes the energy impulses traveling through wires and transforms them back to sound.

Transmission of waves - upon encountering a boundary or different medium, the waves continue to travel into that medium with different speed or wavelength.

Amplitude - the maximum displacement of an oscillation (back and forth movement) from the center position

Equalization - the process of distributing sound evenly and uniformly (i.e. to balance).

Oscilloscope - an instrument that measures variations in fluctuating electrical signals or impulses (i.e. voltage) that is displayed as a visible waveform on the florescent screen of a cathode ray tube.

The Sound Engineer's job is to "mix" the sound - meaning that volume, tone, and reverberation can be manipulated through the soundboard.

Distortion - an inaccurate reproduction of sound or light waves.

Frequency - the number of repetitions of a periodic process in a unit of time; the number of waves (sound or electromagnetic) that pass a fixed point each second.

Pitch - subjective term to identify frequency of a sound wave
Reverberation -the resounding or echo of sound waves.

Preview Discussion
Why does your favorite musical group sound so good on CD or tape?
What do they do to make a CD? Where is it done?
Have you seen a group live that you have heard on a CD? Do they sound different? Why is that?

Post Viewing Activities

Make Your Own Waves
Materials Needed:
2-3 ft of PVC pipe per student
Modeling Clay
Rubber Bands
Sandpaper
Handsaw

Engagement Activity:
Recall the video and discuss the difference between low frequency and high frequency. What sounds did the instruments in the video create? Discuss what makes a guitar string sound higher or lower. (moving the finger up and down the guitar frets shortens or lengthens the string and therefore the sound wave.

Bridge Activity: Hold up two precut pieces of PVC pipe, one long and one short. Ask students to tell which one will produce the higher tone. Why?

Activity:
1. Have students mark the lengths they desire on the pipe with pencil. Five to eight segments may be used.
2. Cut the PVC pipes in different lengths for students.
3. Have students carefully seal one end of each pipe segment with modeling clay.
4. Students should lightly sand the other end of each segment, so it will be smooth.
5. Have students arrange each pipe segment in order, shortest to longest, and rubber band them together.
6. Have students blow across the tops of their new wind instrument. Which length of pipe produces the lowest frequency? The highest?

The Wave Model
Submitted by John Hollis, physics teacher

Materials Needed:
Slinky
Approximately 30 lengths of copper pipe (or similar diameter PVC) cut to various
lengths from 5cm to 25cm
Rulers
Calculators
Electric musical keyboard (a toy store model will suffice)

Recommended Additional Technology:
Oscilloscope and microphone to measure frequencies, or
Vernier or PASCO probeware to capture and display waves

Engagement Activity:
For this particular lesson the teacher may kickoff the
discussion with something like, "Can you see sound waves or are they
invisible?" Discuss how one might model the invisible and investigate it.
During the discussion, make sure to gather your students' prior knowledge of waves, in order to address any misconceptions they may have. Ask for a volunteer to hold the far end of the Slinky on the floor as you shake one end to demonstrate wave attributes of frequency, wavelength, and amplitude. Make standing wave patterns and get the class to count waves out loud as you shake the Slinky. Shake harder, not faster, for greater amplitude.

Throughout this demonstration pose questions:
How many waves do you see?
Where is the motion at maximum?
Which waves have a shorter wavelength?
Is there a connection between frequency and amplitude?

Bridge Activity
Hold up two different pipes. Ask, "Which one will produce
longer waves"?

Exploration (lab activity):
1. Divide students into groups and give each group three different lengths of pipe to measure in meters. "A graph is a mathematical model of the relationship between two variables. Let's graph the relationship between frequency and wavelength. Our independent variable is wavelength since the pipes have been precut to various lengths."

2. Have students hold a finger over the end of a pipe and blow across the other end to produce a sound. "Our wave model suggests this is one quarter of a wavelength, because the finger on one end holds the pipe relatively still just as the student holding one end of the Slinky did. The open end where the air is being blown, is a place of maximum motion and is one quarter of a wave from the fixed end. Students will need to multiply measurements by four to get the wavelengths of the sounds produced.

3. Have one student produce the note by blowing, while another tries to match it on the keyboard. The frequency of the sound (note) on the keyboard can then be determined. Frequency is measured in Hz or 1/seconds. Provide students with a list of musical notes and their respective frequencies:

Middle C or C4 264Hz F4 352Hz
B4 495Hz
D4 297Hz G4 396Hz
C5 528Hz
E4 330Hz A4 440Hz

NOTE: Other ways to determine frequency include the use of the oscilloscope grid or the computer software provided by Vernier or PASCO. Matching tones is easier to do.

4. Have adjacent groups share their data to create a graph, either by hand or on the computer. The graph should show an inverse relationship (a curved line).

Catch More Waves on These Sites

The Physics Classroom
http://www.glenbrook.k12.il.us/gbssci/phys/Class/sound/soundtoc.html

Scientific American Explorations: Physics of Music
http://www.explorations.org/everdaysci01_fall98_pitch.html

Pacific Science Center: Music Physics
http://exhibits.pacsci.org/music/MusicPhysics.html

Acoustical Society of America: Acoustics and You
http://asa.aip.org/acou_and_you.html