Lab: Using Resonance to Calculate the Speed of Sound
Names: _______________
, ________________
Period ____________
Background:
An object resonates when a vibration matches the object’s natural frequency. By identifying the type
of standing wave causing the resonance, knowing the frequency of the vibration and measuring the
dimensions of the object you can determine the speed of sound in the object. In this lab our object will be a
column of air (a tube).
Materials:
Tuning fork
Graduated cylinder
Tube
Meter stick
Water
Procedure:
1. Partially fill the graduated cylinder with water (approximately 70 mL)
2. Place the tube in the graduate cylinder, by moving the tube you can adjust the length of the air column
in the tube.
3. Hold a tuning fork over the tube opening and raise the tube until the sound reaches its maximum
resonance (volume).
4. Measure the length of the empty chamber (the length of the tube out of the water). Record this length
and the frequency on the tuning fork in the table below.
5. Repeat this for at least six different tuning forks.
Length of Tube
(m)
Frequency of
Tuning Fork (Hz)
#1
#2
#3
#4
#5
#6
Questions:
1. Calculate the wavelength inside the tube for the last tuning fork (the standing wave should be a fixed-free
fundamental wave). Show all work including a drawing of the standing wave.
2. Calculate the velocity of sound in the tube using the frequency stamped on the tuning fork and the
wavelength calculated above. (Show all work)
3. Describe the affect of resonance on the tuning fork when place above the tube.
4. Using the speed of sound determined in question #2, what length of empty chamber would you need to
create resonance for a frequency of 64 Hz? (Show all work) This is the opposite of the calculation in
questions #1 & #2.
Complete the EXCEL file on the Lederman drive. Print your first worksheet and attach to this printout.