Frequency vs. Size
Teacher Instructions
Background Information:
Students should have an understanding of sound as a vibration. This could be demonstrated or reinforced by using a small drum to show how striking the head sets up a vibration which in turn caused the air to vibrate. Students also need an understanding of what period and frequency are. (See "Important Information") A good way to present these terms is by measuring them for a simple pendulum as a demonstration.
- The amount of time for one complete swing (full back and forth motion) is the period
- The number of complete swings in a given time (for example one minute) is the frequency
Set-Up:
Exact setup is determined by individual groups. You may want to divide the various types of objects so that all objects are explored.
Procedures:
Exact procedures are determined by individual groups. However insure they are keeping their objects constant. For example if a group chooses to use the metal pipes insure they do not include data from a bottle or a plastic pipe.
Data / Observation:
Since the "Big Question involves pitch and size insure the students are including pitch and size data.
You may want your students to record the time readings used to determine period.Calculations:
- Students should show their calculation of frequency.
- Students should make a graph of frequency versus size.
Conclusions:
- Student's conclusion should be supported by their data and their graphs
- Frequency should go down as the size of the vibrating object increases.
- Students who choose to use a bottle with water may obtain backwards results because they measure the height of the water in the bottle instead of the height of the column of air.
Questions / Post Lab:
- Discuss the time unit used during the experiment. Exactly what is a millisecond? What does this tell you about how fast sound is vibrating?
- Discuss questions raised by the students.
- Assign students to find answers to questions raised.
- Challenge students to use their graphs to predict what a frequency would be between their data points.
- Challenge students to find the relationship between and how tightly a rubber band is stretched and the frequency.
- In music low frequency means a low pitch like a tuba produces. A violin or whistles produce high frequencies. What does your experiment tell you about sizes of musical instruments?
Notes:
- The screen shots and the instructions are for a Macintosh using Vernier equipment and Vernier's Sound Software. You can modify the instructions to fit your equipment.
- The objects listed in the Equipment/Materials section are just suggestions. Almost any object that can be cut into various lengths or that comes in various sizes can be used.
- There are no unusual safety hazards with this experiment.
The Big Question:
How does the pitch (frequency) of sounds change with the size similar objects.
Important Information:
- Period: the amount of time it takes for one complete vibration.
- Frequency = 1 divided by the period
Equipment / Materials:
Basic equipment:
- Computer
- ULI
- Microphone
- Sound program
- Ruler
Materials for Making Sounds
- 2 Liter Soda Bottle and water
- Tuning forks of different sizes
- 1 1/2" or 2" PVC pipe of various lengths
- Different lengths of metal pipe (such as electrical conduit)
Computer Set Up
- Connect the ULI to the computer (use the modem port) and connect the ULI to a power supply.
- Connect the Microphone to DIN 1 on the ULI.
- Turn on the ULI and the computer.
- Open the program "Sound"
- Under the "Display" menu choose "One Graph"
Procedures:
- Click the "Start" button. "Waiting for trigger" will appear at the bottom of the screen.
- Make your sound close to the microphone. A graph of your sound will appear. If it is a good graph click "Stop" to keep temporarily.
- You can select Autoscale under the Display menu to make the graph more readable.
- If you do not obtain a good graph try again.
- Under the Analyze menu Select Analyze Data A. This will place a line on the graph that moves with you mouse. It will also display the time at the bottom of the graph.
- Move the line to the top of one of the peaks as shown in Figure 1 record the time on your lab sheet. Move the line to the top of the next peak as shown in Figure 2 record the time on your lab sheet.
- Measure the size of your object that is making the sound and record on your lab sheet.
- Change the size of the object making the sound. Graph and analyze the sound as done above and record all your data on your lab sheet.
- Continue changing the size of the object making the sound until you have at least 4 data pairs.
Data / Observation:
Clearly record all your data on you lab sheet. Minimally your data should include a description of the class of object used, the size of the object, and the information needed to determine the period and frequency of the object.
Calculations:
- Calculate the frequency of each of your sounds. (Remember period = difference in time between peaks and frequency = 1 / period. Record at least one sample calculation and record all your frequencies on your lab sheet.
- Make a graph of frequency versus size. Use graph paper or "Graphical Analysis"
Conclusions:
What is the relationship between size and frequency? Support your conclusion with your data and calculations.
Student Instructions for LabPro
The Big Question:
How does the pitch (frequency) of sounds change with the size similar objects.
Important Information:
- Period: the amount of time it takes for one complete vibration.
- Frequency = 1 divided by the period
Equipment / Materials:
Basic equipment:
- Computer
- LabPro
- Microphone
- LoggerPro software
- Ruler
Materials for Making Sounds
- 2 Liter Soda Bottle and water
- Tuning forks of different sizes
- 1 1/2" or 2" PVC pipe of various lengths
- Different lengths of metal pipe (such as electrical conduit)
Computer Set Up
- Connect the LabPro to the computer and to a power supply.
- Connect the Microphone to Channel 1 on the LabPro.
- Turn on the computer.
- Open the LoggerPro software.
- Under the Experiment menu choose Show Sensors and select the student force sensor in channel 1.
- Under the Experiment menu choose Data Collection... and select the Triggering tab at the top right. Check the Enable Triggering box and click OK.
Procedures:
- Click the Collect button.
- Make your sound close to the microphone. A graph of your sound will appear. If it is a good graph click Stop to keep temporarily.
- You can select Autoscale Graph under the Analyze menu to make the graph more readable.
- If you do not obtain a good graph try again.
- Under the Analyze menu select Examine. This will place a line on the graph that moves with you mouse. It will also display the time at the bottom of the graph.
- Move the line to the top of one of the peaks as shown in Figure 1 record the time on your lab sheet. Move the line to the top of the next peak as shown in Figure 2 record the time on your lab sheet.
- Measure the size of your object with the meter stick that is making the sound and record on your lab sheet.
- Change the size of the object making the sound. Graph and analyze the sound as done above and record all your data on your lab sheet.
- Continue changing the size of the object making the sound until you have at least 4 data pairs.
Data / Observation:
Clearly record all your data on you lab sheet. Minimally your data should include a description of the class of object used, the size of the object, and the information needed to determine the period and frequency of the object.
Calculations:
- Calculate the frequency of each of your sounds. (Remember period = difference in time between peaks and frequency = 1 / period. Record at least one sample calculation and record all your frequencies on your lab sheet.
- Make a graph of frequency versus size. Use graph paper or a graphing program.
Conclusions:
What is the relationship between size and frequency? Support your conclusion with your data and calculations.
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