Investigation To Find the Speed Of Sound

According to the graph, an increase in the distance causes an increase in the time. This shows that they are directly proportional to each other. There is a very strong trend in the graph, which shows a strong positive correlation. I can tell this because I have drawn a line of best fit. There don’t appear to be any major anomalies since all the points are either directly on the line or close to the line of best fit. This shows that the results are relatively reliable. However, the points that are not directly on the line of best fit could be due to a number of reasons including inaccuracy when hand-drawing the graph or when conducting the experiment. Generally, the speed of sound through air is measured to be 330m/s. The graph enables me to work out the speed which is:

Gradient = rise

run

= 0.4

1400 x 10-6

= 0.4

0.0014

= 286m/s (to 3 s.f.)

I have worked out from the graph that the speed of sound through air is 286m/s (to 3 s.f). Even though this does not match the general speed of sound through air, it is quite close. The inaccuracies could be due to inaccuracy when hand-drawing the graph or when conducting the experiment.

There is sufficient evidence to prove that the experiment was conducted correctly, (though slightly inaccurately) and that the results are reliable.

Evaluation:

From the experiment, I was able to obtain relatively accurate results from which I was able to construct an accurate and informative graph. I feel that the amount of results that I gathered was sufficient for me to come to a reliable conclusion. The results are of a good quality since most of the points are either near or on the actual best fit line. The evidence is suitable for the aim of my experiment since I have found out what I required from the experiment. I also feel that I repeated the experiment enough times and the various distances used were sufficient. In the experiment, the same microphone, the same QED, metre rule and other equipment were used.

Only one variable was changed: the distance between the two microphones. However, I feel that there were a few inaccuracies along the way which could

have affected the overall result. For example, when the microphone was placed over the metre rule, it was not measured accurately and the distance therefore differed. Sometimes, the microphone could have been placed at a slight slant which would project more sound to one side than the other. Also, there could have been background noise which could have affected the overall result of the experiment. When the hammer was hit onto the piece of metal at approximately 10cm, it could have hit the metal with different a different amount of force each time causing a louder sound to reach the QED. Also, the metal was only placed at approximately 10cm and not exactly 10cm. This would have affected the overall result because the distance was not the same each time. To solve this problem, a clamp could be used to clamp the metal in place so that it was exactly 10cm. When the two speakers were placed next to the metre ruler, this was not done accurately, as shown in diagram a:

To solve this, the metre rule should be secured in place on the table with tape to ensure it does not move. Then a mark should be made on the speaker and each time the speaker was moved, the mark on the speaker should match up with the measurement as shown in diagram b:

Other sounds around the room and outside the room could affect the experiment so any background noise should be kept to a minimum since the QED could pick these up.

The graph was plotted with the average results of two experiments so this would also affect the overall result. Instead of just doing two experiments to average, more experiments should be done before averaging it out. This is to give way for any inaccuracies and ensure a larger chance of a more accurate result.

If the experiment was repeated, I would solve the problems I mentioned earlier. I would also repeat the experiment more times to retrieve more accurate results, although I feel that the results I gained were already relatively accurate. However, to obtain a result even closer to the general speed of sound, all of the precautions above should be put into action.

*Joanne Hua*11Jupiter*Mr. Fullman*Physics Coursework*Speed Of Sound*Triple Award Science*