Activity Time: 20 minutes
Recommended Grades: 1 - 5
Objective: Analyze and compare how sound changes as it travels through different mediums. Then, develop and use models to produce a variety of different sounds.

• Wire hanger
• Various strings made of different materials, at least 24” in length
  • yarn
  • fishing line
  • thread
  • metal wire (such as guitar string or artistic wire)
• Optional: Various objects of different materials, to use in place of the hanger. For example, wood, plastic, and metal rulers or spoons

1. Tie the center of the string or wire to the neck of a hanger, leaving an equal length on both sides.
2. Hold one end of the string in each hand, forming a V with the hanger suspended in the middle.
3. Gently swing the hanger into the side of a chair or table, and describe the sound that is produced.
4. Wrap one end of the string around each index finger, and set the tips of your fingers gently into your ears. The hanger will dangle below.
5. As before, gently knock the hanger into a chair or table and note the difference in the sound.
6. Repeat the experiment with different types of strings and make note of the sounds that are produced.
7. Construct an explanation for what you are hearing. As an extension, develop models using hanging objects of other materials. Predict how the sound will change each time.

Sound is nothing more than a vibration that travels in a wave. When this wave reaches our ears, it vibrates our eardrums and we hear a sound. This wave needs a medium through which to travel. As a sound wave travels through a medium, energy has to pass from one molecule to the next. Depending on how close the molecules are to one another, and the tighter their bonds, the faster those vibrations can be transferred between molecules. In the experiment above, the sound had to initially travel from the hanger to your ears through the air, a gas. When holding the string up to your ears, the sound traveled through the string, a solid. Because molecules are spread further apart in a gas than in a solid, the sound produced changed. Similarly, by changing the material of the string, or by replacing the metal hanger with a different object, a variety of sounds are produced.