Hold the wire hanger and tap it with a pen or pencil. Describe the sound.
Tie 40 centimeter lengths of sting onto opposite ends of a hanger. Wrap about 6 centimeters of each string around a finger on each hand. Gently plug the fingers wrapped with string into each ear. Have another person tap the hanger with a pen or pencil or other objects. Describe the sound.
Tap the hanger onto other objects around the room. Do different objects produce different sounds?
Unplug your ears and swing the hanger into some of the same objects as in procedure three. Is the sound different. How? Why?
What causes a sound to begin?
What enables you to hear sound?
Hang other objects, such as metal spoons from lengths of string or from the hanger. Plug the strings into your ears with your fingers and listen to the sound these different objects make when they are tapped.
Replace the string with wire. How do the sounds compare to those when string was used?
Use different types of string to hang objects. Does the sound change with different strings? Which string seems to send the loudest/softest sound to your ears? Why?
Change the string length. Does length affect loudness?
happens if another person touches the string after tapping the object
hanging from it? Why?
When objects vibrate sound is produced. Sound vibrations can travel through solids, liquids, or gases: this vibration is called a sound wave. On a molecular level, as molecules bump against eachother, they transfer the soundwave from one molecule to the next. Thus sound travels from the source to the receiver.
The speed that sound travels depends on the material in which it is traveling and the molecular packing of that material. Molecules are packed most densely in solids and least densely in gases. Molecular packing density in liquids is between solids and gases. The closer the molecules are together, the better sound travels.
In this activity, when the string and fingers were plugged into the ears, the sound traveled better than just through the string and air. In addition, the bones in your head act as a resonators and also vibrate to make the sound fuller. Tightly woven string works better than loosely woven yarn,, especially if the length is over 45 cm.
Another word for molecules is particles.
Sound Site ©1999 Science Museum of Minnesota