Experiment 5: Introduction to Sound

Purpose:
To understand the shapes and characteristics of sound waves. 

Equipment:

• Lab Pro
• Microphone

Experiment:

Using logger pro, collect data while someone says, "AHHHHHH" into the microphone.  Answer the following questions about the graph that is produced:

1)     Would you say this is a periodic wave?  Support your answer with characteristics.

2)     How many waves are shown in this sample?  Explain how you determined this number.

3)     Relate how long the probe collected data to something in your everyday experience. For example: “Lunch passes by at a snails pace.” Or “Physics class flies by as fast as a jet by the window.”

4)     What is the period of these waves?  Explain how you determined the period.

5)    What is the frequency of these waves?  Explain how you determined the frequency.

6)     Calculate the wavelength assuming the speed of sound to be 340 m/s. Relate the length of the sound wave to something in the class room.

7)     What is the amplitude of these waves?  Explain how you determined amplitude.

8)     What would be different about the graph if the sample were 10 times as long? How would your answers for the questions a-g change? Explain your thinking. Change the sample rate and test your ideas. Copy the graph and label it #1h.

Have someone else speak into the microphone and compare and contrast the two graphs. 

Then use a tuning fork to produce a graph and compare and contrast that graph against the human graphs. 

What would you expect if the tuning fork wasn't as loud as the first time?

Conclusion:

Part A:

1)      This wave is periodic since it repeats similar to a sinusoidal wave. 

2)      5.4 waves are in this sample. 

3)      The data was collected over 0.03 seconds which is faster than you blink.

4)      The period of the wave is 0.0056 seconds.  We determined this by dividing the sample time (0.03) by the number of waves (5.4).

5)      The frequency is 180 Hz.  We determined this by 1/T and confirmed it by extrapolating 5.4 waves in .03 seconds and looked at how many waves in one second (frequency).

6)      The wavelength equals velocity divided by the frequency.  (340m/s) / (180 s^-1) = 1.89m.  This is about the length of a desk. 

7)      The amplitude is 1.8 units.  We determined this from the graph.

8)      Everything would be the same except you would have more waves in the sample. 

 

Part B:

The second wave sampling was not as regular as the first.  There are 3.5 waves in the sample which is 0.03 seconds.  The period is 0.0086 seconds.  The frequency of the wave is 116 Hz.  The wavelength is 2.93 m.  The amplitude is 0.75 units. 

Part C:

The tuning fork produces a much more uniform sound wave compared to the human waves.  There are 15 waves in the sample of 0.03 seconds.  The period is 0.0020 seconds.  The frequency of the wave is 500 Hz.  The wavelength is 0.68 m.  The amplitude is 0.23 units. 

Part D:

 

Only the amplitude of the wave changed (decreased) while the other data remained the same.  We changed the impact surface to a softer material (skin/pants vs rubber shoe sole) which resulted in a softer wave.