6. Meter stick
e) Procedure
- Hold the tuner vertically to the cylinder.
- Turn on tuner and set frequency to 512Hz. Hold it horizontally as close to the open end of the tube as you can. Move the stopper up and down until the sound is coming out the loudest.
- Measure the distance (L) from the top of the stopper to the open end of the tube.
- Repeat twice more and record results
- Repeat steps 1-4 with frequencies of 480, 425, 340, 320 and 256Hz.
- Record the data.
g) Procedure for Controlling Variables
- Perform each trial at the same temperature
- Hold tuner in the same constant, non-moving position for each trial
- Hold the mic the same distance away from the tube for each trial
II. Data Collection
Diameter of the tube = 0.025m ± 0.005m
Uncertainty in Frequency = ±1%
Uncertainty in Length = ±0.002m
III. Data Processing
From graph:
Slope = 87.97
Slope = (v/4)
v = Slope×4
v = 87.97 × 4
v = 351.88 m/s
IV. Evaluation
From the above Data Analysis, the speed of sound in air is found to be approximately 351.9m/s. The theoretical value for the speed of sound in air is 343m/s.
Percentage difference = (351.9−343.0)/343.0 = 2.59%
There is this slight difference in results due to the following reasons:
- The lab was not conducted at the right temperature. For the speed of sound to be 343m/s, it needs to be 20C. Temperature could also vary throughout the experiment
- Air could have escaped from the rubber stopper plugging the end. Though it is assumed that the stopped represents a wall for the closed end, it is possible that some air could get through.
- The tuner was held clumsily or at varying lengths to the tube, this would result in the frequency being disrupted.
- The optimum point of wavelength was not reached. Since I was only using my ears, it is quite likely that the length could have been off when measuring.
The results are thus quite close to the accepted value for the speed of sound in air.
V. Conclusion
In this lab, we were able to approximate the velocity of sound waves in air at a given temperature.
This was done quite modestly with the use of a simple tube and tuner. At resonance, the amplitude of vibration at the open end of the tube increases to a maximum. Taking advantage of the linear relationship between the length (L) of the air column and the reciprocal of the frequency of the tuning fork (1/f) to determine the slope of the graph thus obtained. It was then possible to determine the speed of sound, because the slope equaled nothing but (v/4), where (v) is the velocity of sound. Thus the speed of sound was verified
