Sound Waves and Music - Lesson 1 - the Nature of a Sound Wave

Sound Waves and Music - Lesson 1 - The Nature of a Sound Wave : Taken from: http://www.physicsclassroom.com/Class/sound/u11l1a.html and edited by Mr Wolgemuth

Please take your time to *process* this article…don’t just simply blast through it, think about what it means in terms of how you communicate—which is to say how you create and process sound waves.

There are several new words to keep in mind when reading this article: 1. Propagate: To move through (for example a water wave propagates through water, while a seismic wave propagates through the Earth) 2. Medium: The material through which a wave moves. For example sound waves move through the medium of air while water waves move through the medium of water

Sound is a Mechanical Wave Sound and music are parts of our everyday sensory experience. Just as humans have eyes for the detection of light and color, so we are equipped with ears for the detection of sound. We seldom take the time to ponder the characteristics and behaviors of sound and the mechanisms by which sounds are produced, propagated, and detected. The basis for an understanding of sound, music and hearing is the physics of waves. Sound is a wave that is created by vibrating objects and propagated through a medium from one location to another. In this unit, we will investigate the nature, properties and behaviors of sound waves and apply basic wave principles towards an understanding of music.

3. What is the main point of that paragraph? ______

______A wave can be described as a disturbance that travels through a medium, transporting energy from one location to another location. The medium is simply the material through which the disturbance is moving; it can be thought of as a series of interacting particles. The example of a slinky wave is often used to illustrate the nature of a wave. A disturbance is typically created within the slinky by the back and forth movement of the first coil of the slinky. The first coil becomes disturbed and begins to push or pull on the second coil. This push or pull on the second coil will displace the second coil from its rest position. As the second coil becomes displaced, it begins to push or pull on the third coil; the push or pull on the third coil displaces it from its rest position. As the third coil becomes displaced, it begins to push or pull on the fourth coil. This process continues in consecutive fashion, with each individual particle acting to displace the adjacent particle. Subsequently the disturbance travels through the slinky. As the disturbance moves from coil to coil, the energy that was originally introduced into the first coil is transported along the medium from one location to another. Why did the author compare a sound wave propagating through the air to a slinky? In other words, how do air molecules behave like a slinky?

4. ______

A sound wave is similar in nature to a slinky wave for a variety of reasons. First, there is a medium that carries the disturbance from one location to another. Typically, this medium is air, though it could be any material such as water or steel. The medium is simply a series of interconnected and interacting particles. Second, there is an original source of the wave, some vibrating object capable of disturbing the first particle of the medium. The disturbance could be created by the vibrating vocal cords of a person, the vibrating string and soundboard of a guitar or violin, the vibrating tines of a tuning fork, or the vibrating diaphragm of a radio speaker. Third, the sound wave is transported from one location to another by means of particle-to-particle interaction. If the sound wave is moving through air, then as one air particle is displaced from its rest position, it exerts a push or pull on its nearest neighbors, causing them to be displaced from their rest position. This particle interaction continues throughout the entire medium, with each particle interacting and causing a disturbance of its nearest neighbors. Since a sound wave is a disturbance that is transported through a medium via the mechanism of particle-to-particle interaction, a sound wave is characterized as a mechanical wave. Take a few moments to try the following: 5. Turn to the person sitting next to you and discuss the reading so far. What was the main point the author was trying to make? 6. What questions do you still have about sound waves? 7. Discuss those questions with your group and see if you can solve those problems. 8. Now get out a piece of blank paper…. Sketch what was happening in terms of air and soundwaves while you were having that conversation. Include the following in your sketch: a. How did you generate those sound waves? b. How did those sound waves move through the air? c. How did the other members of your group actually hear those sound waves? 9. Now cover your years and say something to the person sitting next to you. d. Why is it that you can actually still hear your friend talking (although not very well). Aren’t you blocking those sound waves from entering your ears? Let’s talk about this with the entire class