Experiment 6: Speed of sound

The purpose of this experiment is to find speed of sound by closed pipes and reflected waves. Sound waves are compression waves that can be reflected back through a pipe.

The speed of sound is the time it takes for the wave to travel the length of the pipe.

Procedure

We performed this experiment by snapping our fingers at the end of a closed pipe and recording the sound of its echo.  We take the time difference between the original wave and the beginning of the reflected wave.  The length of the pipe is 1.32m, but since the wave is reflected it travels twice that length.  The speed of sound is found by the equation  

 In our case 

The data

Trial	Time original wave (s)	Time reflected wave (s)	Time difference (s)	Speed(m/s)	% error
1	0.00426	0.01124	0.00698	378.22	10.08
2	0.00074	0.00736	0.00662	398.79	16.06
3	0.00062	0.00776	0.00714	369.75	7.61
4	0.00078	0.00814	0.00736	358.70	4.39
5	0.0007	0.0076	0.0069	382.61	11.35

The actual speed of sound used for error is v =331+0.60T. T is room temperature. If lab room temperature is 21⁰C, then the speed of sound is 343.6m/s.  This speed is used for error.

Summary

Our measurements for the speed of sound had large error.  It is important to use sound measurements as brief as possible because the speed of sound is big.  The error of the measured time causes big deviations in calculated speed.  If we measured from the fist smallest peak of the echo, we might have gotten better measurements.