THE SCIENCE AND APPLICATIONS OF ACOUSTICS - H. H. Arnold ...

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Then the energy dissipated in a cycle is obtained from∫ 2π20.6 Techniques for Vibration Control 607∫ 2πCẋ 2 (t) d(ωt) = CA 2 ω cos 2 (ωt + φ) d(ωt) = πCA 2 ωω 00The energy dissipated per radian is CA 2 ω/2, and the peak potential energy iskA 2 /2. Therefore, the system loss factor isη s = CA2 ω/2kA 2 /2= CωkIntroducing Equations (20.8) and (20.9), Equation (20.45) becomes(20.45)η s = 2ξ ω ω n(20.46)At resonance, η s assumes the value of 2ξ. This indicates that systems withlarge loss factors are highly damped. For small values of damping, applyingEquations (20.18), (20.28), and (20.29):η S = 2ξ = δ π = 1(MF) resonanceIn the analysis of structural damping, complex stiffness and complex moduliare principal parameters. We recall that the steady-state oscillation is described bythe following expression:which can be rewritten aswhere(−ω 2 m + iωC + k)X = F 0(−ω 2 m + k ∗ )X = F 0k ∗ = k + iωCThe imaginary stiffness is the damping. Employing Equation (20.45), we canexpress the complex stiffness ask ∗ = k(1 + iη s )In an analogous manner, the complex Young’s modulus E for damping materialcan be expressed asE ∗ = E(1 + iη M )where E is the real part of the Young’s modulus of the damping material and η Mis the loss factor of the damping material. 1The loss factors and complex moduli vary with frequency and temperature. It hasbeen assumed that the damping force is proportional to velocity and independentof amplitude, but there are situations where the damping of the materials depends1 η s is the loss factor of the system structure and damping material.
608 20. Vibration and Vibration ControlFigure 20.11. Sound transmission characteristics: (a) incident wave resolving into a reflectedwave and a transmitted wave and (b) transmission loss in a structure as a functionof frequency.mainly on vibration amplitude, so the assumption of viscous damping must beapplied judiciously.Damping converts mechanical energy into thermal energy; and while there area number of mechanisms for such energy conversion, we describe here thosethat are the most useful ones. Damping materials also reduce sound transmission.When a sound wave strikes a structure, causing its surface to vibrate, the vibratingsurface produces a reflected wave and a transmitted wave [Figure 20.11(a)].The transmission loss through the structure varies with frequency as shown inFigure 20.11(b) for a given temperature. The region of damping control nestlesbetween the low-frequency region where stiffness reigns as the controlling parameterand the higher-frequency region where mass predominates as the controllingparameter. Between these two regions, many natural vibratory modes of the structureexist, and this region is the only one where transmission loss depends greatlyupon resonance conditions. Here structural damping is the controlling parameter.Internal DampingA material with very high-damping internal properties could be utilized to eliminatenoise emanating from a structure. Ferromagnetic materials and certain magnesium
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THE SCIENCE ANDAPPLICATIONS OFACOUS
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xPrefaceReferencesBacon, Sir Franci
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xiiContents16. Ultrasonics 44317. C
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2 1. A Capsule History of Acoustics
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1. A Capsule History of Acoustics 5
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12 1. A Capsule History of Acoustic
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14 2. Fundamentals of AcousticsFigu
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16 2. Fundamentals of Acoustics2.2
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18 2. Fundamentals of Acousticsof t
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20 2. Fundamentals of AcousticsQ z+
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22 2. Fundamentals of Acousticsin t
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24 2. Fundamentals of AcousticsWe c
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26 2. Fundamentals of Acoustics(2)
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28 2. Fundamentals of AcousticsEqua
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30 2. Fundamentals of Acoustics11.
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32 3. Sound Wave Propagation and Ch
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3.14 Performance Indices for Enviro
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3.14 Performance Indices for Enviro
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or in terms of complex exponential
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3.17 Sound Intensity 61Here the sur
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3.18 The Monopole Source 63The thre
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3.21 Energy Density 653.20 The Hemi
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References 67medium. The time avera
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Problems for Chapter 3 69(a) the wa
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4Vibrating Strings4.1 IntroductionI
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4.4 General Solution of the Wave Eq
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4.6 Simple Harmonic Solutions of th
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4.7 Standing Waves 77Figure 4.3. Di
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4.8 The Effect of Initial Condition
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4.10 Forced Vibrations in an Infini
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4.11 Strings of Finite Lengths: For
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References 854.12 Real Strings: Fre
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Problems for Chapter 4 878. A devic
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90 5. Vibrating BarsFigure 5.1. A b
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92 5. Vibrating BarsSettingc 2 = E/
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94 5. Vibrating BarsThe allowable f
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96 5. Vibrating Barsthe acceleratio
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98 5. Vibrating BarsFigure 5.5. Loc
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100 5. Vibrating Barsmore difficult
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102 5. Vibrating BarsFigure 5.7. An
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104 5. Vibrating Barsthe light beam
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106 5. Vibrating BarsFigure 5.8. Tr
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108 5. Vibrating BarsFigure 5.10. T
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110 5. Vibrating Barsof 0.005 m dia
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112 6. Membrane and PlatesFigure 6.
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114 6. Membrane and PlatesBecause t
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116 6. Membrane and PlatesThe left-
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118 6. Membrane and PlatesTable 6.1
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120 6. Membrane and PlatesIn real a
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122 6. Membrane and PlatesTable 6.2
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124 6. Membrane and PlatesAt low fr
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126 6. Membrane and PlatesThe elast
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128 6. Membrane and PlatesFor the f
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130 6. Membrane and Plates(b) Deter
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132 7. Pipes, Waveguides, and Reson
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152 8. Acoustic Analogs, Ducts, and
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9Sound-Measuring Instrumentation9.1
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9.3 Microphones 175Figure 9.1. A cu
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SolutionEquation (9.3) is applied t
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9.5 Selection and Positioning of Mi
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9.6 Vector Sound Intensity Probes 1
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9.8 Proper Procedures for Using the
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9.8 Proper Procedures for Using the
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Example Problem 39.10 Dosimeters 18
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9.11 Noise Measurement in Selected
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9.11 Noise Measurement in Selected
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9.12 Real Time Analysis 193analyzer
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9.13 Fast Fourier Transform Analysi
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9.14 Data Windows and Selection of
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9.16 Measurement Error 199whereβ =
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9.18 Measurement of Sound in a Free
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9.20 Sound Power Measurement in a D
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9.20 Sound Power Measurement in a D
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9.23 The Addition Method for Measur
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References 209acoustical output and
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Problems for Chapter 9 2112. Determ
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214 10. Physiology of Hearing and P
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11Acoustics of Enclosed Spaces:Arch
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11.2 Sound Fields 245Figure 11.1. P
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11.4 Sound Intensity Growth in a Li
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11.5 Sound Absorption Coefficients
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11.6 Growth of Sound with Absorbent
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11.7 Decay of Sound 253Following Sa
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11.8 Decay of Sound in Dead Rooms 2
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11.9 Reverberation as Affected by S
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11.13 Sound Levels due to Direct an
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11.15 Concert Halls and Opera House
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Figure 11.9. A view of the Boston S
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11.16 Band Shells and Outdoor Audit
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11.16 Band Shells and Outdoor Audit
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11.17 Subjective Preferences in Sou
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References 277preferred subsequent
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Problems for Chapter 11 279Siebein,
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12Walls, Enclosures, and Barriers12
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12.3 Mass Control Case 283Figure 12
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12.5 Effect of Frequencies on Sound
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12.6 Coincidence Effect and Critica
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12.7 The Double-Panel Partition 289
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an ideal gas) varies in the followi
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12.8 Measuring Transmission Loss 29
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12.10 Combined Sound Transmission C
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12.11 Noise Insulation Ratings 297F
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12.11 Noise Insulation Ratings 299s
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12.12 Noise Reduction of a Wall 301
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12.12 Noise Reduction of a Wall 303
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12.14 Enclosures 305to the extent t
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12.14 Enclosures 307and similarly f
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12.15 Small Enclosures 309walls. Ac
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12.16 Acoustic Barriers 311Figure 1
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12.16 Acoustic Barriers 313In the c
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Equation (12.67) becomes(11D = λ+
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Problems for Chapter 12 3173. A 0.7
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13Criteria and Regulations forNoise
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13.3 The Occupational Safety and He
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13.4 Perception of Noise 323inspect
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13.6 Indoor Noise Criteria 325accou
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13.6 Indoor Noise Criteria 327Room
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13.7 Equivalent Sound Level, Day-Ni
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13.7 Equivalent Sound Level, Day-Ni
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Composite Noise Rating13.9 Rating o
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13.10 Evaluation of Traffic Noise 3
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Highway Construction Noise13.10 Eva
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13.11 Evaluation of Community Noise
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13.12 Guidelines and Regulations in
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References 353Computer Program, HIC
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Problems for Chapter 13 355Problems
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14Machinery Noise Control14.1 Intro
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14.4 Fan or Blower Noise 359Table 1
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14.4 Fan or Blower Noise 361Figure
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14.6 Pumps and Plumbing Systems 367
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14.6 Pumps and Plumbing Systems 369
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14.8 Gears 371fromwheref BRC = N r
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14.8 Gears 373Figure 14.7. Gear noi
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14.8 Gears 375Figure 14.8. Gear tra
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14.8 Gears 377The subscripts 1 and
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14.10 Ball and Roller Bearings 379l
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14.10 Ball and Roller Bearings 381c
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14.11 Other Mechanical Drive Elemen
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Belt Drivesf CL = n 1N 1 2400 × 12
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14.12 Gas-Jet Noise 387said to be c
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14.12 Gas-Jet Noise 389power discha
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Solution14.12 Gas-Jet Noise 391Usin
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14.13 Gas Jet Noise Control 393Solu
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14.13 Gas Jet Noise Control 395Figu
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14.13 Gas Jet Noise Control 397Figu
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14.14 Mufflers and Silencers 399Fig
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(1 + m)A I 1=A 314.14 Mufflers and
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14.14 Mufflers and Silencers 403Let
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References 405Figure 14.21 illustra
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Problems for Chapter 14 407the nois
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15Underwater Acoustics15.1 Sound Pr
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15.3 Speed of Sound in Seawater 411
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15.4 Velocity Profiles in the Sea 4
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15.4 Velocity Profiles in the Sea 4
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15.5 Underwater Transmission Loss 4
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15.6 Parametric Variation of Absorp
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15.8 Underwater Refraction 421Figur
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15.9 Mixed Layer 423When G is const
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15.11 Sonar Transducers and Their P
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Example Problem 115.12 The Sonar Eq
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Active and Passive Equations15.12 T
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15.13 Noise, Echo, and Reverberatio
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15.13 Noise, Echo, and Reverberatio
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15.14 Transient Form of Sonar Equat
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Example Problem 315.16 Shortcomings
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15.17 Theoretical Target Strength o
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Problems for Chapter 15 441Wilson,
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444 16. Ultrasonicscatching small i
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446 16. UltrasonicsPlanck constant
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448 16. UltrasonicsEquation (16.5)
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450 16. UltrasonicsFigure 16.1. Sou
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452 16. Ultrasonicsthe positive hal
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454 16. Ultrasonicson each and ever
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456 16. Ultrasonicscomplete as a li
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458 16. Ultrasonicsinitial of their
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460 16. Ultrasonicsoptic axis, deno
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462 16. Ultrasonicstransducer, it h
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464 16. UltrasonicsTable 16.1. Valu
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466 16. Ultrasonicsthe mechanical r
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468 16. UltrasonicsThe Physics of M
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470 16. UltrasonicsFigure 16.7. The
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472 16. Ultrasonicscurvilinear arra
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474 16. Ultrasonics(a)amplitudeinpu
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476 16. Ultrasonicsslow to allow th
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478 16. Ultrasonics5. In the cases
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480 17. Commercial and Medical Ultr
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510 18. Music and Musical Instrumen
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Figure 18.7. The frequencies of the
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Figure 18.20. The violin octet deve
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Page 561 and 562: 556 18. Music and Musical Instrumen
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Page 585 and 586: 580 19. Sound Reproductiontuned ape
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Page 589 and 590: 584 19. Sound ReproductionDickason,
Page 591 and 592: 586 20. Vibration and Vibration Con
Page 611: 606 20. Vibration and Vibration Con
Page 623 and 624: 618 21. Nonlinear Acousticsby∇ 2
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Page 627 and 628: 622 21. Nonlinear Acousticswhereδ
Page 629 and 630: 624 21. Nonlinear AcousticsThe shoc
Page 631 and 632: 626 21. Nonlinear AcousticsBut the
Page 633 and 634: Appendix APhysical Properties of Ma
Page 635 and 636: Appendix A. Physical Properties of
Page 637 and 638: Appendix BBessel FunctionsB.1 The B
Page 639 and 640: B.8 Tables of Bessel Functions, Zer
Page 641 and 642: Appendix CUsing Laplace Transforms
Page 643 and 644: C.3 Solving Differential Equations
Page 645 and 646: C.4 Equations with Multiple-Order R
Page 647 and 648: SolutionC.5 Equations with Complex
Page 649 and 650: C.5 Equations with Complex Roots 64
Page 651 and 652: SolutionC.5 Equations with Complex
Page 653 and 654: 650 IndexAuditoriums, design of, 26
Page 655 and 656: 652 IndexElectrostatic speakers, 58
Page 657 and 658: 654 IndexKey notation, 518Kinetic e
Page 659 and 660: 656 IndexPascal (unit), 48Percent i
Page 661 and 662: 658 IndexSound intensity growth in
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660 IndexWater-hammer arresters, 37
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