Summary
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Abstract
For centuries, beautiful bell towers, like the Leaning Tower of Pisa, have been the center of village life, announcing the time of day, the joy of weddings, and the sorrow of funerals. They were also used to call villagers to action in times of danger. Have you ever wondered, though, why people put the bells in towers? The bells are so heavy, why haul them all the way up to the top of tall towers? Why not just ring them on the ground? Putting bells up high does make for a dramatic visual display, but is there more to it than that? Does hoisting the bells up high change the way the bell's music sounds to people? In this music science fair project, you'll explore the acoustics of bell towers.Even if you don't have a bell on hand right now, you can get an idea of how a bell's music is heard if you take the lid of an aluminum or stainless steel saucepan and hold it by the handle, with the bottom pointed downward, and strike it with a wooden spoon. First, hold the lid close to the ground, only touching the handle, and strike it with the spoon. Then hold the lid above your head, again with the bottom pointed downward and only touching the handle, and strike it a second time with a similar force and in a similar location as the first time. Do you hear any difference? Think about the high frequencies or high-pitched sounds, and the low frequencies or low-pitched sounds. Can you hear all the high frequencies in both positions? What about all the low frequencies? Do some frequencies seem to be attenuated (or reduced) by moving the lid closer to the ground? Write down your observations in your lab notebook.
To investigate how the music from bell towers is heard, you will need an instrument or CD player, a helper, and access to a home or building that:
- Is away from external sources of noise, like traffic,
- Has at least two higher floors above the ground floor, and
- Has windows that are on all the floors that you want to test.
Be sure to take an adult with you if you have to leave your home. You will play a melody on your instrument, or a well-known instrumental piece of music with high and low notes on your CD player, in front of open windows on each floor, at the same volume. Do not ever lean out the windows, as that is very dangerous. As you play music from each floor, your helper will count paces away from the building or home until he or she can no longer hear certain notes in the melody. Which frequencies are first to be attenuated? High or low? How much farther away can your helper walk before the music cannot be heard at all? Can your helper hear at greater distances when you play the music on the ground floor or on the upper floors? Go wake up Frère Jacques and find out!
Bibliography
- This source describes the history and purpose of bell towers:
Wikipedia Contributors. (2008, October 8). Bell tower. Wikipedia: The Free Encyclopedia. Retrieved October 12, 2008.
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