Introduction
The purpose of this experiment was to determine the speed of sound at room temperature using the microphone connected to a computer. Sound travels at a speed which is comparatively higher than the speed many objects. Consequently, the determination of speed of sound is technically challenging task. Most experiments rely on echo which is a reflection of sound to estimate this speed. The speed of sound at standard atmospheric pressure and temperature of 0º C is 331.5m/s. The experimental value of the speed of sound is expected to be less than the accepted value because low winter temperatures.
Materials and Methods
Materials
- Computer
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- LabPro
- Logger Pro
- Vernier Microphone
- 1 meter tube
- Tape measure
- Thermometer
- Two pieces of wood
- Hard cover book
Procedure
The vernier microphone was plugged into Channel 1on LabPro connected to the computer. The experimental 24 folder in the computer was opened to confirm if a graph of level versus time was displayed. This graph was observed. Thereafter, one end of the tube was closed a hard cover book pressed against the end of the tube. Then, the length of the tube was measured and recorded. The air temperature was also measured and recorded. Microphone was placed as close as possible to the open end of the tube then the data collection processes was started by clicking the Collect. Immediately afterwards, the two pieces of wood were struck to produce sound. This sound was detected by the microphone and a graph was displayed on the computer screen. The Examine button was clicked and the cursor moved between the beginning of the first vibration and the end of echo vibration to determine the time interval between these two points. This time interval was recorded. A total of five trials were conducted the time interval in each trial determined and recorded.
Results
Analysis
The speed (v) is given by distance (d) / time (t)
This can be written as v = d/t
In this experiment, the average time interval was the total time taken by sound to travel from open end of the tube to the closed end and back to the open end. The microphone detected the sound which travelled through the tube. This sound was reflected by the hard cover book and was detected again by the microphone. This was represented on the screen as set of vibrations.
The average time interval is divided by two to get the time taken by sound to travel from one end of the tube to the other end. This is half the total distance travelled by the sound.
Therefore, t =0. 0062 / 2
0.0031s
Speed = 1 / 0.0031
322.6m/s
The percentage error
Expected speed v = 331.5m/s ± 0.6 m/s/ºC
(331.5 – 1.2) m/s
330.3m/s
Relative error = (Expected – Experimental) / Expected
(330.3 – 322.6) / 330.3
0.023
Percentage error
0.023 x 100
2.3%
Conclusion
The experimental value of was below the accepted value as hypothesized. However, the value was not equal to the expected theoretical value. The deviation of 7.7m/s between the expected value and experimental value might have been brought about by experimental errors. One possible source of error was inaccurate determination of the length of the tube. The microphone might not have been as close to the open end of the tube as possible. The other source of error was mathematical in nature. The time interval values were rounded off to four decimal places. Thus, the values used for calculating speed were not the exact values.
This experiment has wide range of application in real world. It is used to estimate the location where enemies’ artilleries are fired from. The process involved in the determination of this location is called sound ranging. The process uses combinations of many microphones located at different positions. The time difference between detection of sound at one point and detection of the sound at another point is used to compute the location of the enemy during war.
