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

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340 13. Criteria and Regulations for Noise ControlTable 13.4. Typical Octave Band Sound Pressure Levels of Automobiles and HeavyTrucks, Measured at 1.2 m Above the Ground at a Distance of 15.2 m.Octave-band center frequency, HzA-weighted sound125 250 500 1000 2000 4000 level, dB(A)Automobile speed56 km/h (35 mph) 65 61 62 61 57 53 6588 km/h (55 mph) 71 68 66 68 66 60 72Heavy truck speed56 km/h (35 mph) 87 84.5 81.5 78 74.5 70.5 83.588 km/h (55 mph) 87.5 85 87.5 82.5 77 73.5 87.53. Heavy Trucks (HT): All vehicles having three or more axles, including threeaxlebuses and three-axle tractors with and without trailers. Generally GVW >12,000 kg (26,000 lb).Table 13.4 shows the octave-band sound pressure levels typical of automobilesand trucks at two different speeds.Measurements are made by vehicle type for each selected speed ±5 km/h. Fora given category of vehicles at a given speed, the reference energy emission levelis given byL 0 = L 0mean + 0.115L 2 0SDwhere L 0mean is the arithmetic average emission level for the specific categoryand speed and L 0SD is the standard deviation of that emission level.Vehicle Noise Prediction According to the FHWA ModelOn the basis of many measurements, FHWA developed a model for predictinghighway noise (Barry and Reagan, 1978). We first compute the reference meanlevel [(L 0 ) E ] i for each vehicle type i. This level represents a speed-dependent valueof the average (energywise) of the maximum passby levels measured at a referencedistance of 15.2 m (50 ft) for a given vehicle type. The U.S. Federal reference meanemission levels are computed from:Automobile: (L 0 ) E = 38.1 log(S) − 2.4 dB(A)Medium trucks: (L 0 ) E = 33.9 log(S) + 16.4 dB(A)Heavy trucks: (L 0 ) E = 24.6 log(S) + 38.5 dB(A)where S is the average operating speed in km/h.Adjustments for Traffic Conditions(13.14a)(13.14b)(13.14c)A number of adjustments have to be made to the reference mean emission levelscomputed through the use of Equations (13.14). These adjustments are for (a) the
13.10 Evaluation of Traffic Noise 341traffic density, (b) distances to areas of human activity, (c) finiteness of roadwaysegments, (d) presence of road gradients, (e) shielding by buildings, (f) shieldingby rows of trees, and (g) barrier attenuation.The traffic flow adjustment ( traffic ) i is rendered to account for the hourly flowof vehicle type i and to average the level over a 1-h time period as follows:( traffic ) i = 10 log (N i d 0 /S i ) − 25 dB(A) (13.15)whereN i = hourly flow rate of vehicles of type i, vehicles/hd 0 = the reference distance of 15.2 mS i = speed of the ith vehicle type, km/hDistance adjustment takes into consideration the type of ground cover (e.g.,sound will attenuate more readily over a soft surface than over a hard parking lotpavement). Field data gathered by FHWA have shown an average rate of attenuationto be approximately 4.5 dB(A) per doubling of distance over a grassy surface andan attenuation of 3.0 dB(A) per doubling of distance over a paved surface. Thesetwo rates are used by FHWA to establish a ground cover parameter called analpha factor (α). For hard sites, the alpha factor has a value of zero; for soft sites, itassumes the value 0.5. The distance adjustment distance can be generally expressedas distance = 10(1 + α) log(d 0 /d)where d is the perpendicular distance from the receiver to the center of thetravel lane. Table 13.5 provides guidance on when to use propagation rates of 3.0or 4.5.The methodology described above assumes an infinitely long road. In analyticalpractice, highways are subdivided into a series of straight segments of finite length.Table 13.5. Guidelines for Choosing Sound Propagation Rates.Situation1. All situations in which the source or the receiver are located 3 mabove the ground or whenever the line of sight a averages morethan 3 m above the ground2. All situations involving propagation over the top of a barrier3 m or more in height3. Where the height of the line of sight is less than 3manda. there is a clear (unobstructed) view of the highway, theground is hard, and there are no intervening structures, orb. the view of the roadway is interrupted by isolated buildings,clumps of bushes, or scattered trees, or the interveningground is soft or covered with vegetationPropagation rate,dB(A)3(α = 0)3(α = 0)3(α = 0)4.5 (α = 1/2)a The line of sight (L/S) is a direct line between the noise source and the observer.
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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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Page 303 and 304: 12.11 Noise Insulation Ratings 297F
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Page 317 and 318: 12.16 Acoustic Barriers 311Figure 1
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Page 323 and 324: Problems for Chapter 12 3173. A 0.7
Page 325 and 326: 13Criteria and Regulations forNoise
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Page 331 and 332: 13.6 Indoor Noise Criteria 325accou
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Page 359 and 360: References 353Computer Program, HIC
Page 361 and 362: Problems for Chapter 13 355Problems
Page 363 and 364: 14Machinery Noise Control14.1 Intro
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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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570 19. Sound ReproductionAlbert, a
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572 19. Sound ReproductionD. Magnet
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574 19. Sound Reproductionon, machi
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576 19. Sound ReproductionIt is fai
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578 19. Sound ReproductionINNER SUS
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580 19. Sound Reproductiontuned ape
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582 19. Sound Reproductionuse of MP
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584 19. Sound ReproductionDickason,
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586 20. Vibration and Vibration Con
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618 21. Nonlinear Acousticsby∇ 2
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620 21. Nonlinear Acousticsmay be i
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622 21. Nonlinear Acousticswhereδ
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624 21. Nonlinear AcousticsThe shoc
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626 21. Nonlinear AcousticsBut the
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Appendix APhysical Properties of Ma
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Appendix A. Physical Properties of
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Appendix BBessel FunctionsB.1 The B
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B.8 Tables of Bessel Functions, Zer
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Appendix CUsing Laplace Transforms
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C.3 Solving Differential Equations
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C.4 Equations with Multiple-Order R
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SolutionC.5 Equations with Complex
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C.5 Equations with Complex Roots 64
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SolutionC.5 Equations with Complex
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650 IndexAuditoriums, design of, 26
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652 IndexElectrostatic speakers, 58
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654 IndexKey notation, 518Kinetic e
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656 IndexPascal (unit), 48Percent i
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658 IndexSound intensity growth in
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660 IndexWater-hammer arresters, 37
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