Like all our lab exercises, the waves and sound lab will use aPhET simulator. Some of these simulators require you to enable Javaor Flash. You can download and use the simulator on your desktop,or for some labs you can run it in your browser. Preferred browsersettings and system requirements can be found at the “Running Sims”FAQ:  https://phet.colorado.edu/en/help-center/running-sims(Links to an external site.)

For this lab, we’ll use the “Sound Waves” simulator:

https://phet.colorado.edu/en/simulation/legacy/sound (Links toan external site.)

This is a Java sim and will require a download of the software.Start the simulator, and spend some time learning the interface. Wewill be using the \"Listen to a Single Source\" and \"Measure\"tabs, socheck out the interface in both. Understand the sliders, the pausefunction, and the measurement functions before you begin.

1. Use the Listen to a Single Source tab in Sound Wavesto start your investigation of sound. Click Audio enabledso you can hear the sound.

• When you adjust the frequency on the slider, how does the soundchange? How does the visual model of the wave change? Write yourobservations.
• When you adjust the amplitude on the slider, again observe howthe sound changes and how the visual representation of the waveformchanges, and record your observations.
• Do you think the frequency on the slider perfectly matches thevisual waveform, or is some adjustment being made for thevisualization? Describe what you think this adjustment might be,both qualitatively and in terms of the wave equation y ( x , t ) =y m sin ⁡ ( k x − ω t ).

2. Sound is produced when something vibrates; this movementcauses disturbances in the surrounding air pressure. Investigatehow the speaker cone moves to produce different sounds. Then,explain the relationships between the movement of the speaker coneand the sound that is made; include drawings to support yourexplanation. Record your observations and attach any necessarysketches as screenshots.

3. Use the tools on the Measure tab to find the speed of soundin air. Use the relevant equations to find which measurements youcan make to discover the appropriate value.

Using a data table like the one below, record severalmeasurements (at least 6-8 to minimize variance) of wavelength andfrequency.

Trial	Wavelength (m)	Frequency (Hz)
1
2
3
4
5

4. Graph your data points in Excel or another graphingapplication, making sure to choose axes such that you get the speedof sound as the proportionality constant of the line. Refer to thewave speed equation to confirm this. Then, perform a fit to theline. Show the equation of the trendline on your graph and discusswhether you think the data you took accurately describes therelationship between wave speed, wavelength, and frequency.

Compare the value you found in your line fit to the actual,published value for the speed of sound in air, and include apercent error calculation. You can find the given value in severalplaces, including your textbook and the internet - just make sureto cite your source properly. Use a temperature of 20 degreesC.

5. If you wanted to know the period of a wave,and did not have the frequency slider information available, couldyou find it with the tools in the simulator? Describe the methodyou would use to find the frequency (i.e. which measurements youwould take, and which calculations you would perform).

6. Now, test the method you developed in part 5. Choose twofrequencies and use your method to find the period. Record:

• the measurements you took, with appropriate units
• the calculations you did for each frequency.

Also, check to see how close you got - since period is theinverse of frequency (T = 1 f) then you can verify how well yourmethod works. If it didn't work, describe any changes you wouldmake to improve the results.

Lab Report:

Your lab report should be a typed document, with any necessarysketches or graphs attached as scans or picture files.

For the Sound Waves lab, hand in the following:

Part (a): Your preliminary observations and drawings from parts1 and 2.

Part (b): Your data table and graph from part 3, and yourcalculated average speed, discussion of possible error, andcitation for published speed of sound from part 4.

Part (c): A full description of the method you developed to findthe period of a wave without knowing its frequency, including whatmeasurements you would take and what calculations you would use.Also, your test of the method in full for two separate frequenciesand your discussion of any errors and any changes you would make tothe method.