Awards Earned: 3rd Place, 6th Physical Science, PCA Science Fair

Which materials carry sound waves best?

I think a rubber band will carry sound waves the best because it stretches.

Different string materials: string, rubber band, copper wire.

To see if air can carry sound waves, measure signal received at microphone without cups and string at each test frequency while keeping the same distance between the speakers and the microphone.

8oz plastic cups, string, rubber bands, copper wire, microphone, oscilloscope, signal generator, speakers

1] Put one hole on the bottom of two 8-ounce plastic drinking cups.
2] Take a 2-meter long string, put the ends through the holes, and tie the ends.
3] Do the same with 2 meters of copper wire and the rubber band.
4] Connect a microphone to the oscilloscope.
5] Connect a speaker to the signal generator.
6] Set the signal generator to 1000 hertz.
7] Hold one cup to the speaker and one cup to the microphone.
8] The oscilloscope will show the wave that arrives at the second cup.
9] Measure and record the wave amplitude on the oscilloscope.
10] The bigger the wave, the more sound has traveled through the type of string.
11] Repeat the above tests for each type of string at a number of frequencies from 200 hertz to 2,000 hertz.
12] At each frequency, before testing any of the strings, hold the microphone in front of the speaker to measure the wave amplitude leaving the speaker. Then compare the wave amplitude for the cups and strings to this baseline amplitude.

I found that the string carried the most sound, copper wire was in second, and the rubber band was in last place. No measureable wave arrived at the microphone for the control group at all frequencies.

My hypotheses was incorrect. I thought the rubber band would carry the most sound because it vibrates the most, but because it vibrates it dampens the sound. I found that sound travels the best through string. In some of my tests, the string carried more sound than the baseline. I do not know why this happened. Perhaps it was because the baseline was measured without the cups. String came in first for carrying sound, second was copper wire, next was the rubber band, and in last came air. I also found that sound traveled better in the range of two hundred fifty hertz through one thousand hertz.

For my experiment I attempted to find which materials carry sound the best. As string or wire carry sound, we want to be sure to carry God's Word to everyone.

Mark 16:15 says, “And he said to them, go into all the world, and preach the gospel to all creation.”

These verses tell us to spread the gospel to the entire world no matter what they look like or the problems they have. Some materials may carry sound better than others, but they all have the ability to carry sound. God gives us all the ability to spread the gospel whether it be in singing, preaching, or doing service for Christ. We should use all of our abilities to bring others to Christ.

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