Look at the stage of a rock ‘n’ roll concert and you’re likely to see a wall of speakers. Get close to these speakers and you’ll discover that they are big, really big. Big speakers have a larger vibrating surface than smaller speakers. This larger surface area can transfer vibrations to many more air particles than a smaller surface area. As the numbers of these vibrating particles increase, so does the volume!
Things Required:
Tuning fork
Large flat surface (such as a tabletop)
A friend
Directions:
Strike a tuning fork against your knee. Hold it at an arm’s length. Can you hear the pitch it produces? Ask a friend to stand across the room. Can he or she also hear the sound of the vibrating fork?
Now strike the tuning fork again. As it vibrates, place the base of the handle firmly against a large flat object, such as a tabletop or chalkboard. What happens now?
Experiment with the surfaces of different size and composition. What characteristics make a surface boost the loudness of a sound? What characteristics make an object muffle the loudness of a sound?
This Is What Happens:
As the tuning fork vibrates, it transfers its vibration energy to the surrounding air particles. As you can see, the arms of the tuning fork are quite small. Therefore, they are not in direct contact with a great deal of particles. Sounds produced solely by the vibrating fork aren’t loud.
When the fork is placed against a large surface, such as a tabletop, things change. As the fork continues to vibrate, its vibration is transferred to the tabletop.
Because of its size, the tabletop is in contact with many more air particles than the tuning fork.
As this greater number of particles are set in motion, a much louder sound is produced. As you investigate materials, you’ll find that hard surfaces that are free to vibrate are great for boosting sound volumes. In contrast, materials that cannot vibrate are poor boosters of sound.
