Master Handbook of Acoustics About the Authors F. Alton Everest was a leading acoustics consultant. He was cofounder and director of the Science Film Production division of the Moody Institute of Science, and was also section chief of the Subsea Sound Research section of the University of California. Ken C. Pohlmann is well known as an audio educator, consultant, and author. He is professor emeritus at the University of Miami in Coral Gables, consultant for many audio manufacturers and car makers, and author of numerous articles and books including Principles of Digital Audio. Contributions are included from Peter D’Antonio, Geoff Goacher and Doug Plum. Master Handbook of Acoustics F. Alton Everest Ken C. Pohlmann Fifth Edition New York Chicago San Francisco Lisbon London Madrid Mexico City Milan New Delhi San Juan Seoul Singapore Sydney Toronto Copyright © 2009, 2001 by The McGraw-Hill Companies, Inc. All rights reserved. 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Alton Everest This page intentionally left blank Contents Introduction . xvii 1 Fundamentals of Sound . 1 The Sine Wave . 2 Sound in Media . 3 Particle Motion . 3 Propagation of Sound . 4 Speed of Sound . 5 Wavelength and Frequency . 6 Complex Waves . 7 Harmonics . 8 Phase . 9 Partials . 12 Octaves . 12 Spectrum . 14 Electrical, Mechanical, and Acoustical Analogs . 17 2 Sound Levels and the Decibel . 19 Ratios versus Differences . 19 Expressing Numbers . 20 Logarithms . 21 Decibels . 21 Reference Levels . 23 Logarithmic and Exponential Forms Compared . 24 Acoustic Power . 25 Using Decibels . 27 Example 1: Sound-Pressure Level . 28 Example 2: Loudspeaker SPL . 28 Example 3: Microphone Specifi cations . 28 Example 4: Line Amplifi er . 29 Example 5: General-Purpose Amplifi er . 29 Example 6: Concert Hall . 29 Example 7: Combining Decibels . 30 Measuring Sound-Pressure Level . 30 Sine-Wave Measurements . 31 3 Sound in the Free Field . 33 The Free Field . 33 Sound Divergence . 33 Sound Intensity in the Free Field . 34 vii viii Contents Sound Pressure in the Free Field . 35 Examples: Free-Field Sound Divergence . 36 Sound Fields in Enclosed Spaces . 37 Hemispherical Field and Propagation . 38 4 The Perception of Sound . 39 Sensitivity of the Ear . 39 Ear Anatomy . 40 The Outer Ear . 41 Directional Cues: An Experiment . 41 The Ear Canal . 41 The Middle Ear . 42 The Inner Ear . 44 Stereocilia . 45 Loudness versus Frequency . 46 Loudness Control . 48 Area of Audibility . 48 Loudness versus Sound-Pressure Level . 49 Loudness and Bandwidth . 51 Loudness of Impulses . 53 Audibility of Loudness Changes . 54 Pitch versus Frequency . 54 An Experiment in Pitch . 55 The Missing Fundamental . 56 Timbre versus Spectrum . 56 Localization of Sound Sources . 56 Binaural Localization . 58 Law of the First Wavefront . 59 The Franssen Effect . 59 The Precedence Effect . 60 Perception of Refl ected Sound . 61 The Cocktail-Party Effect . 63 Aural Nonlinearity . 63 Subjective versus Objective . ..