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Unformatted text preview: Physics 1240 Hall Chapter 1 Notes 1 Focus questions and learning goals Chapter 1 focus questions: 1. What is the connection between music and acoustics? 2. What are the physical characteristics of sound? Chapter 1 learning goals. After studying this chapter, you should be able to: 1. Describe waves. (a) Represent waves in various ways, especially using graphs. (b) Describe how small particles in the medium are moving for various kinds of waves, such as sound or ripples on the surface of a pond. 2. Predict how the speed of sound will change if you change various aspects of the sound itself or the room. For example, how does the speed of sound change if you: (a) Raise the pitch? (b) Make the sound louder? (c) Heat the room? 3. Predict how the pitch and loudness of a sound you hear will depend on the frequency and amplitude of a pure tone from a sound synthesizer. 4. Calculate the distance from a source (for example, a lightning strike) if you hear a sound at a different time than you see the even that caused it. 2 Acoustics and Music This course will start with some big questions about sound and music. What is sound ? How do you define music ? How do acoustics fit in? This is partly definitions (that is, human conventions) which I’m not so concerned about: it’s the ideas that matter! Sound can be defined in different ways. It can refer to a physical disturbance (a pressure wave ) that travels from a source. It can also refer to your sensation when that pressure wave wiggles hair cells in your inner ear. (The difference between these two definitions is the essence of the old puzzle that asks “If a tree falls in a forest, and there is no one there to hear it, does it make a sound?”) 2.1 The three ingredients We’ll need to study three things to get a handle on sound: 1. The source, or creation, of sound waves. 1 Physics 1240 Chapter 1 notes 2. The nature of these waves, and how they are transmitted. 3. The detection mechanism (usually this is your ear). This is it—that’s what this course is all about. We’ll talk about all three ingredients, first at an overview level for the first month or so of the term. We’ll then circle back with more details and specifics, maybe even several “passes” at deeper levels, as we go through the course (see the figure in the preface of the book). 2.2 Acoustics Acoustics is the science of sound . It’s a branch of physics—like studying light, or electricity, or liquid crystals. There are people who study acoustics for a living (about 7000 members of the Acoustics Society of America). Acoustics sometimes is related to psychology (what sounds good), sometimes engineering (designing better sonograms for medicine), and sometimes it’s pure physics (understanding the wave phenomena from a source). Topics of study in acoustics might involve health (speech, hearing), perception (neural processing, auditory illusions), architecture (sound mitigation), sound reproduction, and digital synthesis, just to name a few.mitigation), sound reproduction, and digital synthesis, just to name a few....
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This note was uploaded on 08/24/2010 for the course PHYS 1240 taught by Professor Holland,murray during the Spring '08 term at Colorado.
- Spring '08