VRIJE UNIVERSITEIT BRUSSEL Acoustics - the Dept. of ...

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viCONTENTS2.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 302.3.2 Development of the ear with age . . . . . . . . . . . . . 302.4 The human perception of sound . . . . . . . . . . . . . . . . . 312.4.1 The phon . . . . . . . . . . . . . . . . . . . . . . . . . 312.4.2 The sone as measure of loudness . . . . . . . . . . . . . 313 Measuring sound 333.1 Introduction: why measure sound . . . . . . . . . . . . . . . . 333.2 The measurement microphone . . . . . . . . . . . . . . . . . . 333.2.1 Size of the microphone . . . . . . . . . . . . . . . . . . 353.2.2 The sound field where measurements take place . . . . 363.2.3 Influence of the wind speed . . . . . . . . . . . . . . . 373.2.4 Division of sound in frequency bands . . . . . . . . . . 393.3 Frequency weighting of microphone signals . . . . . . . . . . . 413.4 The sonometer . . . . . . . . . . . . . . . . . . . . . . . . . . 423.5 Calibration of measurement systems . . . . . . . . . . . . . . . 443.6 Presence of the observer . . . . . . . . . . . . . . . . . . . . . 443.7 Background noise . . . . . . . . . . . . . . . . . . . . . . . . . 453.8 Quantitative parameters . . . . . . . . . . . . . . . . . . . . . 463.8.1 The equivalent sound pressure level . . . . . . . . . . . 463.8.2 Sound Exposure Level . . . . . . . . . . . . . . . . . . 473.8.3 Statistic sound levels . . . . . . . . . . . . . . . . . . . 473.8.4 The Noise Rating value . . . . . . . . . . . . . . . . . . 483.8.5 The nuisance of fluctuating sound . . . . . . . . . . . . 493.9 The intensity meter . . . . . . . . . . . . . . . . . . . . . . . . 503.10 Measuring sound sources . . . . . . . . . . . . . . . . . . . . . 523.10.1 Measurements in an anechoic half-space . . . . . . . . 523.10.2 Measurements in a full anechoic room . . . . . . . . . . 543.10.3 The comparison method . . . . . . . . . . . . . . . . . 553.10.4 Power measurement with an intensity meter . . . . . . 55II Noise control 574 Sound Absorption 594.1 Acoustic transmission between two media . . . . . . . . . . . . 594.1.1 Normal incidence . . . . . . . . . . . . . . . . . . . . . 604.2 Realization of acoustic absorption . . . . . . . . . . . . . . . . 644.2.1 Plate on an air layer . . . . . . . . . . . . . . . . . . . 644.2.2 Helmholtz resonator . . . . . . . . . . . . . . . . . . . 654.2.3 Porous acoustic absorbing materials . . . . . . . . . . . 67
CONTENTSvii4.3 Measuring the acoustic absorption . . . . . . . . . . . . . . . . 704.3.1 Reverberation time . . . . . . . . . . . . . . . . . . . . 704.3.2 Measuring the absorption in a reverberation room . . . 754.3.3 Measuring the absorption in the Kundt tube . . . . . . 754.4 The direct and diffuse sound field . . . . . . . . . . . . . . . . 775 Sound Insulation 815.1 Measuring sound insulation . . . . . . . . . . . . . . . . . . . 815.1.1 Measuring airborne sound insulation . . . . . . . . . . 815.1.2 Measurement of impact sound . . . . . . . . . . . . . . 845.1.3 Single number rating . . . . . . . . . . . . . . . . . . . 855.2 Airborne sound insulation of a wall . . . . . . . . . . . . . . . 865.2.1 Simple law . . . . . . . . . . . . . . . . . . . . . . . . . 865.2.2 Effect of the wall stiffness . . . . . . . . . . . . . . . . 885.2.3 The coincidence effect . . . . . . . . . . . . . . . . . . 905.2.4 Insulation of double wall constructions . . . . . . . . . 925.2.5 Insulation of a composite wall . . . . . . . . . . . . . . 945.3 The acoustical barrier . . . . . . . . . . . . . . . . . . . . . . 956 Noise control 996.1 Origin of noise . . . . . . . . . . . . . . . . . . . . . . . . . . . 996.2 Reducing noise at the level of the sound source . . . . . . . . . 1026.2.1 Aerodynamic noise sources . . . . . . . . . . . . . . . . 1026.2.2 Sources of hydrodynamic noise . . . . . . . . . . . . . . 1056.2.3 Sources of structure-borne noise . . . . . . . . . . . . . 1086.3 Tackling noise transmission . . . . . . . . . . . . . . . . . . . 1106.3.1 Transmission of aerodynamic noise . . . . . . . . . . . 1106.3.2 Hydrodynamic noise transmission . . . . . . . . . . . . 1126.3.3 Structure-borne noise transmission . . . . . . . . . . . 1136.4 Radiation noise . . . . . . . . . . . . . . . . . . . . . . . . . . 115III Noise directives 1197 Directive 2000/14/EG : ’Machines in open air’ 1238 Noise on the work floor 1278.1 Previous guideline . . . . . . . . . . . . . . . . . . . . . . . . . 1278.2 Present guideline: directive 2003/10/EG . . . . . . . . . . . . 1298.3 Risk of hearing damage . . . . . . . . . . . . . . . . . . . . . . 1328.4 The audiometric examination . . . . . . . . . . . . . . . . . . 135
Page 1: VRIJE UNIVERSITEITBRUSSELAcousticsB
Page 4 and 5: iiWhen sound becomes noise, it will
Page 7: ContentsI Introduction to acoustics
Page 11: Part IIntroduction to acoustics1
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56 CHAPTER 3. MEASURING SOUND
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Chapter 4Sound AbsorptionAll(constr
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4.1. ACOUSTIC TRANSMISSION BETWEEN
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4.1. ACOUSTIC TRANSMISSION BETWEEN
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4.2. REALIZATION OF ACOUSTIC ABSORP
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4.3. MEASURING THE ACOUSTIC ABSORPT
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Chapter 5Sound InsulationWhen consi
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5.1. MEASURING SOUND INSULATION 83F
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5.1. MEASURING SOUND INSULATION 85F
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5.2. AIRBORNE SOUND INSULATION OF A
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5.3. THE ACOUSTICAL BARRIER 95For t
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5.3. THE ACOUSTICAL BARRIER 97Figur
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Chapter 6Noise control6.1 Origin of
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6.1. ORIGIN OF NOISE 101Figure 6.2:
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6.3. TACKLING NOISE TRANSMISSION 11
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6.4. RADIATION NOISE 115Figure 6.17
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6.4. RADIATION NOISE 117Figure 6.20
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Part IIINoise directives119
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124CHAPTER 7. DIRECTIVE 2000/14/EG:
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128 CHAPTER 8. NOISE ON THE WORK FL
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140 CHAPTER 9. COMMUNITY NOISE2. No
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142 CHAPTER 9. COMMUNITY NOISE
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144 APPENDIX A. MATERIAL PROPERTIES
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152 BIBLIOGRAPHY[12] Bruel and Kjae
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