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Timeline: Soundwaves

U.S. Public Domain
These wavy lines illustrate various frequencies (or cycles per second). Sound is a pressure wave transferring energy from one place to another; for example, an instrument to your ear.

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Originally aired on December 11, 2017

Picture yourself at the beach watching the waves rise and break over the sand. You can see the water gather and rise as each waves comes in. Once a wave breaks the water level drops again. You watch the peaks and valleys rolls onto the beach. These waves transfer huge amounts of energy from one place to another traveling through the water and displacing it. We call this a mechanical wave because it needs to travel through a medium, in this case water. The number of waves that crash during a specific period of time is called the frequency.


Sound is also a mechanical wave yet we usually experience it traveling through air and not water. It’s harder to observe sound waves in the same way as ocean waves but they react in a similar fashion. First, something has to vibrate. So, let’s imagine a tuning fork. On its own it does nothing. But, when the fork is struck it is given energy and it releases it by moving back and forth, these motions push and pull the air around it transferring its energy and creating what we call a pressure wave. There are places of higher concentration and lower concentration of air particles and these peaks and valleys of pressure are the wave itself. A tuning fork has been manufactured to move at a specific speed, pushing the air around it at a predetermined rate to create the desired sound waves. The number of waves that pass through your ear at a given interval of time is the frequency of the sound.

We measure frequency in cycles/waves per second. And we’ve decided that when we hear 440 sound waves per second that audible frequency is the musical note “A”. When an orchestra is tuning up before a performance they are manipulating their instruments, tightening strings, moving valves in order to agree that when they apply energy to their instruments, through their lips or a bow, to play “A”, they are vibrating at 440 cycles per second.

When you listen to the orchestra, or any music for that matter, you are allowing the energy, the sound waves of the instruments, to roll over you like waves on the ocean. The delicate bones and flesh in your ears move back and forth with the air around them, recreating the same vibration in your own head. The energy of the instruments has passed to you. That is how sound works.

I break this mechanism down, because I don’t want you to miss the significance to the observer or the audience in this transaction of music making. Waves on the ocean transfer energy from one place to another. Sound waves do the same thing. The energy that comes from a musical instrument is not intended to just float away into the air, it is meant to be listened to, observed. So, allow music to move you. Notice how the sound gathers and rises as each wave comes. Listen for the peaks and valleys as they roll through your ears. There is a tremendous amount of energy being transferred from one place to another.

Timeline is an exploration into the development of Western music.

James Stewart is Vermont Public Classical's afternoon host. As a composer, he is interested in many different genres of music; writing for rock bands, symphony orchestras and everything in between.
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