Lab 11: Waves and
Sound
University of Michigan
Physics Department
Mechanics and Sound Intro Labs
A wave is defined as any periodic disturbance that propagates through
a medium. An understanding of waves that you will gain from this lab
will be invaluable in your further studies of physics. Today you will
investigate sinusoidal waves on a string and in a resonance tube in the
form of standing waves.
 You will use
plastic tubes to
study standing
waves. You can
adjust the length of
the tube using the
plunger to create
“open-closed”
systems.
You will first explore transverse waves on a string. For this purpose,
you have been provided with a mechanical oscillator and a frequency
driver. You will need to attach a string to the oscillator and hang it
over a pulley to attach a mass hangar to the string. You will also need
to make sure that the frequency generator is connected to the wave
driver by banana cables. In this portion of the lab, you will record the
frequencies of the normal modes on the string for three different
tensions, which can be adjusted by adding or removing mass from the
hangar.
The sine wave generator
The wave driver
You will next explore longitudinal waves in a tube. You will see a 4foot long resonance tube on your table. It will have a speaker at one
end and a plunger in the other for adjusting the length of the pipe
cavity. You will need to take the banana cables from the mechanical
oscillator and insert them into the banana jacks on the speaker. You
will use a microphone attached to a meter stick to investigate the
standing waves of sound inside the tube. Please keep your amplitudes
low because the sound becomes very loud when you find the
resonance frequency.
 The speaker used in today’s
lab. Be considerate of your
classmates and GSI by
keeping the speaker
amplitude low.
You will also have a chance to directly calculate the speed of sound in
air. You will need to snap or click something near one end of the
‘open-closed’ tube. You will then observe the echo pulse and use this
information to directly calculate the sound speed in air. That’s all
there is to it!
 Clapping, snapping, or
using a dog training clicker
should all produce an
acceptable sound speed
measurement.
After this lab, you will have gained a great insight into the workings of
waves and sound. Waves are so important in physics that this lab
may be one of the most important to your study of physics all
semester. You will definitely see these concepts again when you study
light next semester.
^ The principle of linear superposition will be very important in
your future studies of light.