Newbury Park High School - Physics
Experiment: Resonance Tube
You will perform 3 different experiments at this lab station. They are numbered 1, 2, and 3. Experiment 1 has a part A and a part B.
Experiment 1: In this experiment you will find several resonant frequencies of the tube. Part IA:
- Set the slider/plunger to the right of the tube at 0.80m. Keep this position constant for this part of the experiment.
2. Set the signal generator to produce a sine wave of frequency 1500 Hz. Push in the “1k” frequency selector button. The oscilloscope should display both the speaker output, and the tube microphone output (See picture next page). Be sure the microphone amplifier switch is turned on. You will be able to tell when the tube is in resonance when the sound level output from the microphone suddenly increases at a particular frequency.
- Slowly lower the frequency from the signal generator, observing several resonance frequencies. Record each resonant frequency in your data. Try to find the lowest possible resonance frequency. It should be in the range of 300 to 400 Hz.
Part 1B: In this experiment you will remove the plunger from the tube, putting the tube into an open end configuration.
1. Remove the plunger from the tube. This is done by sliding off end support on the right side of the tube.
2. Repeat the procedures from experiment 1A, starting at step #2.
3. Again try to find the lowest possible resonance frequency. This time it should be in the range of 100 to 200 Hz
Experiment 2: In this experiment the frequency is held constant and the slider/plunger is moved.
1. Replace the plunger back in the tube.
2. Set the signal generator to produce a sine wave of about 800 Hz.
3. Starting at the end opposite the speaker, move the slider/plunger slowly towards the speaker while observing the display on the oscilloscope.
4. Record the plunger position for all resonance frequencies you observe.
Experiment 3: In this experiment you will measure the time it takes a sound wave to travel the length of the tube to the plunger and return. Then by measuring the total distance traveled, the speed of sound may be calculated.
1. Set the plunger to a position of 0.80 meters.
2. Set the signal to produce a square wave of frequency about 10 Hz. To do this, press the square wave button and the “100” button. (see page 1 of the directions). At this point you should hear clicking coming from the speaker.
3. Increase the sweep speed on the oscilloscope until you get a pattern like the one here.
4. At this point you should be
able to see both the original
pulse of sound from the speaker, and the
return echo of the sound bouncing off the plunger.
5. Set the oscilloscope cursers to measure time, as you did in the speed of light lab previously, and measure the time between the speaker pulse and the return echo.
6. To measure the speed of sound, take the total path length for the sound, which is twice the tube length, and divide it by your measured time value.
7. Look up the actual value for the speed of sound in air, and compare your value to the accepted value by calculating a percent error.
Analysis:
Lab 1A: Closed End Tube
Using the formula…
Calculate the predicted resonant frequencies for the first odd 7 frequencies of your tube. (n = 1 to 13) (Or, as many as you have)
(note that only odd harmonics are present)
N / Calculated frequency / Measured frequency / Percent Error1
3
5
7
9
11
13
Lab 1B: Open End Tube
Using the formula…
Calculate the predicted resonant frequencies for the first 8 frequencies of your tube. (n = 1 to 8) (Or, as many as you have)
N / Calculated frequency / Measured frequency / Percent Error1
2
3
4
5
6
7
8
Experiment 2: Constant Frequency, Variable Length
Using the formula…
Calculate the first several predicted resonant lengths for your tube. (n = 1 to 7 odd numbers --- Or, as many as you have)
N / Length (Calculated) / Length(Experimental) / Percent Error
1
3
5
7
9
Experiment 3: Speed of sound
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