Standing Sound Waves in a Closed Pipe
Purpose: Determine the speed of sound in air.
Materials Needed:
- Safety Glasses—Mandatory
- Aluminum tuning forks of 8 different frequencies (listed on forks)
- Green rubber actuator
- Resonance tube (mm increments)
- 1000 mL cylinder
- ~900 mL – 1000 mL water
Procedure:
1. Record the temperature of the room (there’s a thermometer at the front of the room on the bulletin board). Make sure that you check and record the temperature of the room approximately every 10 minutes in class.
2. Fill your graduated cylinder to approximately 800 mL with water.
3. Place the resonance tube upside-down into the graduated cylinder (the 0.0 cm mark should be at the top)
4. Strike one of the tuning forks (as demonstrated in class) with the rubber actuator. (NOT on the table or on your shoe or anything else!)
5. Place the vibrating end of the tuning fork over the resonance tube, as shown in the diagram. Be very careful not to hit the glass tube with the vibrating metal. The vibrating end of the fork should be approximately 1 cm above the resonance tube.
6. Move the column and the tuning fork up and down until you hear the loudest tone. Record this length of the air column. Make sure the tuning fork remains the same distance above the opening of the resonance tube.
7. Repeat steps 3 – 5 with the same tuning fork for an appropriate number of trials.
8. Repeat steps 3 – 6 for all remaining tuning fork frequencies.
Data Analysis and Evaluation
Complete a full data analysis and evaluation (same rubric/score sheet that we used for the Moment of Inertia lab).
Note: Accepted value for the speed of sound can be found using the average temperature of the room:
v=331+0.6T
Where v is the speed of sound in m·s-1 and T is the temperature of the air in °C.