Sound travels better in water than in air

	Project title: Sound travels better in water than in air
Difficulty level:	Middle school
Main link:	None

Hypothesis:

Sound waves travel better in water, than in the air.

Materials:

- balloons
- air pump
- tape
- foam sheets (1 inch thick at least), about 3 feet by 3 feet in area

The Procedure:

In this experiment, to find out how effectively sound travels through different substances, I filled balloons with these substances, and listened to as many words "spoken" through the balloon, as may be possible.

Variables:

The control variables for this experiment were:

- the method of testing the effectiveness of sound travel
- the participants/helpers involved in the testing
- the type of balloon used for the experiment
- the room temperature

The independent variable is the substance used to fill the balloon. The dependent variable is number of words that can be heard. To measure the dependent variable, we use our observation/hearing.

Procedure:

1. Fill 3 balloons separately with air blown from the mouth, air from a pump, and water

2. Cut out the shape of each balloon from a thick large sheet of foam (that acts as a "wall")

3. have someone hold the foam erect, whilst you place the balloon into the hole.

4. Tape the balloon so that it doesn't move.

5. Have someone very softly whisper words on one side of the foam "wall", close to the balloon.

6. Record all the words that you hear.

7. Do the same experiment with each of the three balloons.

Results:

The results of my experiment show that the balloon filled with water was the best conductor of sound. The balloon inflated by mouth came second. Therefore, the hypothesis should be accepted.

Reasons: Sound waves travel in a more focused pattern in denser media, such as water. Air from our lungs contains carbon dioxide, which is denser than the air in our surroundings. That's why the sound travelled more effectively in the balloon filled with the carbon dioxide.