Note: This lab requires you to listen to sounds played from both YouTube videos

Note: This lab requires you to listen to sounds played from both YouTube videos as well as the simulation. Please let me know immediately if this is an issue in any way shape or form, as I am happy to accommodate/work with you as needed.
We will use the following external links for this lab:
PhET Wave Interference SimulationLinks to an external site.
A3 220 Hz Sound Reference (YouTube)Links to an external site.
C4 261.63 Hz Sound Reference (YouTube)Links to an external site.
A4 440 Hz Sound Reference (YouTube)Links to an external site.
Part 1: What are Sound Waves?
Open the simulation and select the “Waves” tab.
On the right side of the simulation, select the speaker icon.
Do not check the “Play Tone” box yet, as we want to look at this with high amplitude for a bit and it gets really loud. Alternatively, do check the “Play Tone” box at the risk of your earbuds/ headphones/ ear drums.
Slide “Amplitude” all the way to “max,” and press the green button on the speaker (left side of sim).Question 1: Describe the motion of the yellow speaker membrane. How does it relate to the waves shown by the simulation? Switch the display setting on the right from “Waves” to “Particles.”Question 2: Describe what you observe in terms of the motion of the particles and the motion of speaker membrane. How does the speaker membrane affect the motion of the particles?
Question 3: Pick any red air particle and follow its motion. Describe the motion of the individual particle. Does it ever escape its local area? Or does it oscillate back and forth? Does it have the exact same motion every time? How does the speed of that particle change over time?
Question 4: Using your above observations, describe what you might think the definition of a sound wave might be. Consider the following definition of sound waves: Sound waves are longitudinal pressure waves in any material medium regardless of whether they constitute audible sound. (Definition from Merriam-Webster.)Question 5: What parts of the motion of the air particles in the simulation are “high pressure” and which parts are “low pressure?”
Part 2: Frequency and Amplitude
Turn “Amplitude” down to zero and check the “Play Tone” box.Optionally, you can change the display to be waves/particles/both however you would like.
Gradually increase the amplitude slider.Question 6: Describe what you hear while changing amplitude. Is there another common name that we use for the amplitude of a sound wave?
Set the amplitude to a comfortable hearing level. It should be easy to hear but not be too harsh on your ears.
Gradually slide “Frequency” to “max.”Question 7: Describe what you hear while changing frequency. Do we have another common name for the frequency of a sound wave?
Open the three reference sound YouTube links. Question 8: Which of these sounds the same as the simulation? Note: Frequency in the simulation should still be set to “max.”To hear the difference I recommend hitting play on one of the YouTube references, going in to the simulation and pressing play. Then you can pause/play the sim as needed to see if they sound the same.
Pause the sound of all reference videos and the simulation.
Slide frequency to “min” in the simulation.
Play the A3 220 Hz reference.
Press play within the sim. Gradually (very slowly this time) increase frequency in the sim by about 1 mark on the slider.Question 9: Describe what you hear while increasing frequency.The name for this phenomenon is “beat frequencyLinks to an external site.” if you want to look in to it more.
Gradually (very slowly again) decrease frequency in the sim to “min.”Question 10: Describe what you hear while decreasing the frequency back towards min.
Part 3: Finding middle C
Pause your audio reference/simulation as needed.
At the end of Part 2 we observed beat frequency. Assuming that the “low” frequency is equivalent to a 220 Hz A3 (it isn’t perfect, but it is quite close) then we can determine from our above experiment that the beat frequency gets faster as you move the frequency slider away from the reference note, and it gets slower as you move towards the reference note.
Play the C4 reference video.
Use the above strategy to find “Middle C” aka C4 @ 261.63 Hz on on the frequency slider within the sim.Question 11: For this question, submit a screenshot of the frequency slider where you found middle C.