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84 CHAPTER 5. SOUND INSULATIONand thus :R = L p1 −L p2 +10log S A(5.3)where the sound pressure level measurements are performed in tertsoctavebands (according to the international standard ISO 140). Also thetotal absorption A of the receiving room must be measured in terts-octavebands. Above equationis onlyvalid forthelaboratorymeasurement of soundinsulation of a wall (or door, window, panel, ...), whereby no flanking transmissiontakes place. The problem of the measurement of sound insulationbetween two rooms in a construction still persist. Although in this case onehas flanking transmission, it is proposed in international standard to usethe same expression (Equation 5.3) in that case, but with the surface of theseparating wall S replaced by A 0 = 10m 2 open window area :R = L p1 −L p2 +10log A 0A(5.4)Now one can compare different constructions independently of the receivingroom total absorption. The expression T is also used instead of A 0,0.5 Awith T the reverberation time of the receiving room (0.5 sec is a referencereverberation time that is typical for small rooms).5.1.2 Measurement of impact soundThe international standard ISO 140-6: 1978 describes the measurement ofimpact soundinsulationinalaboratory. Animpact device isused(see Figure5.3). It has 5 small steel hammers with normalized mass of 0.5 kg and aradius of 3 cm (the final radius is 50 cm). These hammers are aligned (0.4 mtotal length). At impact of the hammers one measure the normalized soundpressure in the receiving room :L n = L+10log A A 0(5.5)with L the A weighted SPL. Such as was the case for airborne sound insulationone measure also the standardized level (according to ISO-7 140) :L ′ nT= L+10log0.5T(5.6)
5.1. MEASURING SOUND INSULATION 85Figure 5.3: Device for measurement of impact sound insulation with fourhammers indicated by the arrows.5.1.3 Single number ratingIn the measuring procedures for acoustic insulation, described in previousparagraph (ISO 140 series), measurements are performed of the sound pressurelevels in the source-and receiving room in octave bands (or eventuallyterts- octave bands).If we want to make a statement about the insulation quality of a constructionthere is a need for a single number rating which can be compared with referencevalues. Calculation of this single number rating based on measurementsof sound insulation in octave bands is described in ISO 717-1 1982 standard.The procedure includes following steps :The measurements in octave bands or terts bands are plotted in agraph.On this same graph reference values for sound insulation are displayed(see Table 5.1.3).The reference values are shifted in steps of 3 dB until an average differenceof 1 dB with the measurements is obtained.The value at 500 Hz is recorded as single number rating (further, deviationsof more than 8 dB between the shifted reference graph and themeasurements are to be reported in addition to the value at 500Hz).
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VRIJE UNIVERSITEITBRUSSELAcousticsB
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iiWhen sound becomes noise, it will
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ContentsI Introduction to acoustics
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CONTENTSvii4.3 Measuring the acoust
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Part IIntroduction to acoustics1
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4 CHAPTER 1. FUNDAMENTAL CONCEPTS O
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10 CHAPTER 1. FUNDAMENTAL CONCEPTS
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24 CHAPTER 2. THE HUMAN HEARING SYS
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134 CHAPTER 8. NOISE ON THE WORK FL
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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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