Notes on Acoustics
Written by a noted authority in the subject area, this book is a comprehensive study of the theory and practical application of acoustics to numerous fields.
TABLE OF CONTENTS Notes on Acoustics
Chapter 3: Sound Waves
Unlike electromagnertic waves, elastic waves require a gas, liquid, or solid for transmission. Both longitudinal and travsevers waves are involved as will be discussed in this chapter.
Classical mechanics is often divided into two major parts, Kinematics and Dynamics. We follow the same major outline in this chapter and start with wave kinematics, examples, and description of waves.
In dynamics, forces enter into the discussion and the elastic properties of the material substance (gas, liquid, solid) that carries the wave need to be discussed. The underlying physics involved are the conservation laws of mass and momentum to which is added the equation of state for the material (the latter contains information, which, in a sense, is analogous to the spring constant in a mass-spring oscillator).
The interaction of waves with boundaries leads to the phenomena of reflection, absorption, transmission, diffraction, and scattering, which will be treated in separate sections.
3.1 Kinematics
3.1.1 Traveling Waves
As a familiar example consider the waves frequently observed amongst the spectators of a football game in the packed stands. The wave can be generated, for example, by repeating the motion of the spectator to the left, lifting an arm, for example. There is some time delay involved in this repeated motion. As a result, a wave traveling to the right is generated. The speed of the wave depends on the reaction time of the individuals and inertia. For the motion suggested, the wave will be transverse. It should be noted that the wave does not...
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