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Whether you find it soothing or grating, your response to the sound of a violin starts with its production of waves. A violinist can play by drawing a bow across the strings or by plucking them with a finger. Either way, the strings vibrate. The vibrations move through the air until they reach your ears, and you interpret them as sound. It's easy to see how plucking a string makes it vibrate. The finger physically moves the string, and when the violinist lets go, the string moves back. The string's momentum carries it past its original position, and when it runs out of steam, it reverses direction. This back-and-forth pattern, known as periodic motion, goes on until the string's energy is spent and it stops moving. The violin's bow is a little trickier to visualize. A sticky substance called rosin coats the bow, increasing the friction between the bow and the string. This friction lets the bow grab onto and move the string. When the string's tension is too much for the bow's friction to overcome, the string breaks free and moves in the opposite direction. Eventually, if the violinist keeps moving it, the bow can refresh its grip on the string, which reverses direction again and moves with the bow. The essential back-and-forth movement of the bowed or plucked string is known as a standing wave. Imagine two children holding a jump rope between them. With a flick of the wrist, the children move each end of the rope rhythmically up and down. The rope forms a smooth arc, with its highest (or lowest) point in the middle. The very ends of the arc -- the children's wrists -- are completely still. Although there are lots of factors involved in the particular sound of a violin, that's the basic movement of its strings. They move in a regular, back-and-forth arc between two stationary points. If the violinist wants to make a louder sound, he or she moves the bow faster, causing the string to move farther. In other words, the player increases the wave's amplitude. To play a higher note, the violinist shortens the string by pressing it down with the finger. This shortens the wave's frequency. These are the same terms used to describe the sound waves that travel from the violin to your ear. |
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