Generate a transverse pulse and observe the slinky. Now generate a longitudinal pulse. Describe the motion of the wave, and the motion of a single point on the slinky, for both types of waves.

The speed of propagation (or wave speed) is the speed at which the pulse moves. In the table below, mark the distance travelled and time taken for each of the two types of pulses (using a meter stick and a timer), and calculate the wave speed. Make sure you are doing this consistently – i.e. following the leading edge of the pulse, for example.

Now investigate what affects the wave speed. Determine the answers experimentally, e.g., do two more trials. Vary the amplitude (how far you move it from the rest position) between trials. Calculate the speed each time, enter below, and respond to the questions below.

1. Install the program Audacity on your computer, or login to a lab computer which should have the program already installed.
   1. install link: https://www.audacityteam.org/download/
2. Download the linked audio file titled “inclass_speed_100ft.wav” from the course Moodle page, and open it in Audacity. You should see 4 different realizations of the clapping sound of a clipboard. In each, you will see a waveform of amplitude that decreases with time:
   1. 
3. Use your cursor to select one of the sound waveforms, and go to “View” and “Zoom to selection”. This is what you should see (I have highlighted the third sound here for clarity):
   1. 
4. Place your cursor at the beginning of the loud sound, click, and drag it to the position of the echo. At the bottom of your screen, where you can read the time at the position of your cursor, select “Start and Length of Selection” and below that, in the slot where the readings show, select “hh:mm:ss + milliseconds”. Read the length of the time interval off the screen. Do this for all 4 repetitions, and record each time interval reading in the table provided below.
5. I was standing at a distance of 100 ft from the wall when I did this measurement. What is the total distance travelled by the sound between the time it was generated and the time when the echo was recorded? Record this in the table below – it should be the same for each trial.
6. Find the speed of sound for each trial and record it in the table below.
7. Find the average of the four speed trial measurements in the speed column, and record this in the last row in the column below.

Materials needed:

• A computer/device with a microphone, and Audacity loaded.
• A means to make a loud sharp sound. This could be a yell. You are looking for an echo.
• Access to an open area with a wall (such as the outside wall of your building)

1. Make sure your computer’s microphone is turned towards the wall.
2. Measure the distance from your computer to the all off of which you are recording an echo, and record this in Table 2 below.
3. Use Audacity’s “Record” mode to start recording, and do 4 quick repetitions of the loud sound, then stop recording. The recorded wave should resemble the first figure in this worksheet, with a decreasing amplitude. Make sure you can identify the main sound and its echo. If not, repeat the measurement.
4. Using the methods of Part 1, measure the time interval between the sound and its echo for all four repetitions, and record them in Table 2 below.
5. Calculate the speed for all 4 trials, and record them in column 4 of Table 2 below.
6. Calculate the average of all four speed measurements and enter this in the table below.
7. Save your audacity file as a .wav file and upload it to Moodle. Label it by your team number.

On the online spreadsheet linked below (and from our course Moodle page), use one row to enter your team number in column A. Enter the distance you used in column B and your measurement of the average speed from the table above in column C.

https://docs.google.com/spreadsheets/d/1LCwiRrdsa6wZLM_X4pFZ-QkeU0ykxBP8uwJYeAkPyUE/edit?usp=sharing