Experiment 5: Introduction to Sound

Purpose: determine the characteristics of sound waves such as the period, frequency  wavelength, speed, amplitude. Then test variations of its frequencies by having different people speak into the microphone.

Materials:

• Lab Pro microphone
• computer

Experiment:

1. Say “AAAAAAAA” smoothly into the microphone and hit Collect. Once you get a graph that you think is quality, copy it to a Word document and label it #1.  Answer the following questions in your document.

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

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

c)       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.”

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

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

f)       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.

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

h)      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.

                                       

2.  Now have someone else in your group say “AAAAAA” into the microphone.  Copy the graph and label it #2.  Compare and contrast the two people’s wave patterns.  Be specific in your answer. For example: determine the characteristics that you did for the first person (# of waves, frequency, period, amplitude, and wavelength) and include any qualitative observations. 

                                                                                

	# of waves	frequency (Hz)	period (s)	amplitude (arbs.)	wavelength (m)
Trial 1	4	154	0.0065	0.7715	2.21
Trial 2	4	125	0.0080	0.7560	2.72

The first trial was a female voice and the second trial was a male voice. The male voice had a lower pitch which accounted  for the lower frequency and larger wavelength.

3.  Collect data for a tuning fork by striking it on a soft object. Copy the graph and label it #3.  Compare and contrast the waves made by human voice.

	# of waves	frequency (Hz)	period (s)	amplitude (arbs.)	wavelength (m)
Trial 1	4	154	0.0065	0.7715	2.21
Trial 3	12	400	0.0025	0.1620	0.85

In the same amount of time collected, the tuning fork made 3 times as more waves as the first person did. The frequency was 3 times as higher and the wavelength was 3 times as smaller.

4.  If you use the same tuning fork to collect data for a sound that is not as loud, what changes would you expect on the display from the sample in #3?  Test your ideas. Copy the graph and label it #4. What did you do to make the sound softer?  Compare and contrast the waves collected for the louder sound.

We tapped it lighter on our hands to make the sounds softer. We expected all the characteristics to be the different.

	# of waves	frequency (Hz)	period (s)	amplitude (arbs.)	wavelength (m)
Trial 3	12	400	0.0025	0.1620	0.85
Trial 4	7	250	0.0040	0.2835	1.36

Everything changed in the softer wave. Since the frequency changed all the other characteristics changed with it.