Teacher Notes
1. This set of labs was developed using the Vernier LabQuest 2 with two Vernier Microphones. See the
attached appendix for setup instructions. You may have to adapt certain aspects of the labs if you use
a different data collection instrument.
2. For your convenience, two wav files are included.
a. One 1-sec pulse (440 Hz) plays a single 440 Hz tone for exactly one second
b. Continuous 0.5-sec pulses (440 Hz) plays a 0.1-s pulse every half-second for thirty seconds.
3. It is most effective to play the continuous pulses and allow students to take data as they will. A data
set taken at 10,000 samples/sec will take a while to process. For this reason, setting a data duration of
2 seconds is necessary to avoid long delays. If a continuous 0.5s pulse is playing, a student is
guaranteed to record a pulse without having to time the signal and data collection with any degree of
precision.
4. It might be useful to instruct students that it takes a few minutes for the data to compile and display
on screen. It might further be useful to instruct students that no amount of violence against the
computer will speed up this process.
5. Also included is a small PowerPoint file containing post-lab discussions for each lab. We emphasize
post-lab because we feel it will be most useful for students to approach these labs with the challenge
of having to figure out the method rather than simply walking through the steps of a method already
written out.
6. Although the full procedures are written out here, we encourage you to withhold these from students
and instead give them challenges like, “Find a way to measure the distance of separation of these two
microphones” or “Measure the velocity of a moving microphone using interferometry.”
7. Lastly, we encourage the improvement of these labs. If you have an idea for a new lab or a
modification of an old lab that really worked for you, please email us and let us know.
Sincerely,
Daniel Jibson
Alyssa Miller
djibson@westwood.k12.ma.us
amiller2@k12.somerville.ma.us
A Step-by-Step Guide for Using the LabQuest 2 with Vernier Microphones
General Instructions:
1) Turn Labquest on by pushing the power button
2) Plug in both microphones into the CH1 and CH2 slots
3) On LabQuest, press network button and connect to the your network
4) Locate the Data Sharing Source Address (ex: http:// 10.10.1.234). Enter the source
address in the address bar of the browser of any network-connected computer.
5) After your data is collected, highlight the relevant portion of the graph and double
click to zoom in.
6) Press the info button at the bottom left of the graph to change parameters such as
titles, axis labels, axis ranges, etc.
7) Save your image by pressing the download button and clicking “Save as image”
Clearing Data:
1) On the LabQuest, select the Table menu button
2) Select the Table dropdown and choose “Clear All Data”
Change Sample Rate/Size:
1) On the LabQuest, press the Sensor menu button
2) Click the Sensors dropdown and select “Data Collection…”
3) Change Rate, Interval, and Duration as needed
Zero Sensors
1) On the LabQuest, select the Sensor menu button
2) Click the Sensors dropdown and select “Zero…”
Button
Calibration
Procedure:
1. Place two microphones a known distance apart (ex. 0.5 m).
2. Place a speaker in line with the two microphones so that the three make a single straight line.
3. Set the sampling rate to at least 10,000 samples/second and the sample duration to 2 seconds.
4. Begin playing a sound file that plays a 440 Hz pulse every 0.5 seconds.
5. After starting the pulses, take a data sample. Your data should look something like this:
6. By zooming in on the beginning of a single pulse, you should be able to see that the two signals have
been offset because of the separation.
7. Measure the time difference between the same peak as it occurs in each microphone. Be sure to take
measurements of several different peaks and average them to get an accurate Δt.
8. Calculate the speed of sound by dividing the distance of separation by Δt. Use this value as the speed
of sound for every measurement you make today.
Determining Distance of Separation
Activity 1
1.
2.
3.
4.
Record the value you are using as the speed of sound. vsound = ____________
Place two microphones a random distance apart and a single speaker in line with the microphones.
Set the sampling rate to at least 10,000 samples/second and the sample duration to 2 seconds.
Record a pulse and measure the time difference (Δt) between the same pulses recorded by each
microphone. Measure the difference between several peaks and record the average.
5. Calculate the separation between the two microphones using Δt and vsound.
Data
Record the Δt for at least five different peak pairs, average them, and calculate the separation (Δx):
Activity 2
1. Keep the exact same spacing between the microphones as you had in Activity 1 but move the speaker
so that it is no longer in line with the mics (but make sure it is at the same elevation)
2. Set the sampling rate to at least 10,000 samples/second and the sample duration to 2 seconds.
3. Record a pulse and measure the time difference (Δt) between the same pulses recorded by each
microphone.
4. Using the diagram below as a hint, calculate the distance of separation (Δx) in terms of the angle θ,
Δt, and vsound.
Data
Analysis
1. Should the value for Δx be the same in Activity 1 and Activity 2? Explain your answer.
2. Calculate the percent difference between the two values for Δx and state whether the result verifies
the statement you made in question 1.
3. Real interferometers use light signals from distant galaxies to measure their separation distance.
Given that light travels at 3 × 108 𝑚/𝑠, calculate the delay your receivers would record if they were
measuring light instead of sound.
4. How accurate (how many decimal places) would a clock need to be in order to precisely measure
light signal delays?
Determining Velocity of a Receiver
Procedure
1.
2.
3.
4.
Place two microphones at the same location and place a speaker facing the microphones.
Set the sampling rate to at least 10,000 samples/second and the sample duration to 2 seconds.
Begin playing a sound file that plays a 440 Hz pulse every 0.5 seconds.
At the same time that you start taking data, move one of the microphones at least 1 meter away from
the other in 2 seconds.
5. You should have recorded 4 pulses on both microphones that look something like this:
6. Zoom in on the first pulse and measure the difference in time between each peak (see diagram
below). Average several time delays and record that average as Δt for the first pulse. Record Δt as
well as the total time elapsed since the first pulse (which will be 0 for the first pulse).
7. Repeat step 6 for each of the next three pulses. Record all results in the data table below.
Data
1. Using your time data and the speed of sound, record the separation distance of the microphones for
each pulse.
vsound = ___________
Pulse #
1
2
3
4
Average Delay Time
Elapsed Time since First Pulse
0
Δx
2. Graph the values for elapsed time and Δx below (time should go on the x axis).
3. Using the graph, determine the average velocity of the moving microphone. Show your work on the
graph as well as below for any calculations you make.
Analysis
1. Is the value you got for microphone velocity a reasonable one? Explain your answer.
2. If there were two radio dishes looking at a radio source, the measured time delay would give a
straight line distance of separation through the globe instead of along it. Assume that the situation
below depicts Earth and Δx was calculated to be 4358 km. How far apart along the surface of the
globe are the two radio dishes? (You will have to do some research to get information that is not
given here).
3. These two telescopes measured their Δx every few days for several years and discovered that the
distance between them is steadily increasing by about 1 cm / year. What would explain this motion?
Two Islands
The “baseline” (B), or straight-line distance between two receivers, can be determined by pointing them at the
same source. Determine the angle of separation (θ) between the other receiver and the source as well as the
time delay (t) between the signals. Then use trigonometry to solve for B, noting that you can use the speed of
the signal (vsound) with the delay time to calculate the distance the signal travels from one receiver to the next.
1. Using the diagram and instructions, show how to calculate B assuming you know θ, t, and vsound
2. Picking one desk as the “Mainland” measure the distance between that desk and two other “Island”
desks somewhere else in the classroom. Using the chart on the next page,
a. Indicate an appropriate scale.
b. With an arrow, indicate “North” (which, for us, is the direction to the main whiteboard)
c. Map the position of the two islands to scale.
d. Indicate the general direction of the source you used.
(Hint: You can measure θ by placing a piece of paper under your receiver and drawing lines in the direction
of the source and the other receiver)
3. Once you have drawn a map, your teacher will cause an “earthquake” which will shift the position of
the islands. On the same chart above, but in a different color, remap the two islands relative to the
mainland and determine how far and in which direction they moved.
Distance Moved
Island 1
Island 2
Direction Moved