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<p>This part of <std std-id="iso:std:iso:140:en" type="undated"><std-ref>ISO 140</std-ref></std> specifies two series of methods (element methods and global methods) for measurement of the airborne sound insulation of façade elements and whole façades, respectively. The element methods aim to estimate the sound reduction index of a façade element, for example a window. The most accurate element method uses a loudspeaker as an artificial sound source. Other, less accurate, element methods use available traffic noise. The global methods, on the other hand, aim to estimate the outdoor/indoor sound level difference under actual traffic conditions. The most accurate global methods use the actual traffic as sound source. In addition, a loudspeaker may be used as an artificial sound source. An overview of the methods is given in <xref ref-type="table" rid="tab_1">table 1</xref>.</p><p>The element loudspeaker method yields an apparent sound reduction index which, under certain circumstances [e.g. taking account of measurement precision (see <xref ref-type="sec" rid="sec_7.1">7.1</xref>)], can be compared with the sound reduction index measured in laboratories in accordance with <std std-id="iso:std:iso:140:-3:en" type="undated"><std-ref>ISO 140-3</std-ref></std> or <std std-id="iso:std:iso:140:-10:en" type="undated"><std-ref>ISO 140-10</std-ref></std>. This method is the preferred method when the aim of the measurement is to evaluate the performance of a specified façade element in relation to its performance in the laboratory.</p><p>The element road traffic method will serve the same purposes as the element loudspeaker method. It is particularly useful when, for different practical reasons, the element loudspeaker method cannot be used. These two methods will often yield slightly different results. The road traffic method tends to result in lower values of the sound reduction index than the loudspeaker method. In <xref ref-type="app" rid="sec_D">annex D</xref> this road traffic method is supplemented by the corresponding aircraft and railway traffic methods.</p><p>The global road traffic method yields the real reduction of a façade in a given place relative to a position 2 m in front of the façade. This method is the preferred method when the aim of the measurement is to evaluate the performance of a whole façade, including all flanking paths, in a specified position relative to nearby roads. The result cannot be compared with that of laboratory measurements.</p><p>The global loudspeaker method yields the sound reduction of a façade relative to a position 2 m in front of the façade. This method is particularly useful when, for different practical reasons, the real noise source cannot be used. The result cannot be compared with that of laboratory measurements.</p><table-wrap id="tab_1"><label>Table 1</label><caption><title>Overview of the different measurement methods</title></caption><table cellpadding="0" cellspacing="0" frame="box" rules="all" style="border-collapse: collapse;border:solid 2px;" width="650"><colgroup><col align="center" valign="top" width="5%"/><col align="left" valign="top" width="15%"/><col align="left" valign="top" width="20%"/><col align="left" valign="top" width="20%"/><col align="left" valign="top" width="40%"/></colgroup><thead style="border-bottom:solid 2px;"><tr><th style="padding:0 5.20px 0 5.20px;">No.</th><th style="padding:0 5.20px 0 5.20px;">Method</th><th style="padding:0 5.20px 0 5.20px;">Reference</th><th style="padding:0 5.20px 0 5.20px;">Result</th><th style="padding:0 5.20px 0 5.20px;">Field of application</th></tr></thead><tbody><tr><td style="padding:0 5.20px 0 5.20px;"/><td style="padding:0 5.20px 0 5.20px;"><bold>Element</bold></td><td style="padding:0 5.20px 0 5.20px;"/><td style="padding:0 5.20px 0 5.20px;"/><td style="padding:0 5.20px 0 5.20px;"/></tr><tr><td style="padding:0 5.20px 0 5.20px;">1</td><td style="padding:0 5.20px 0 5.20px;">Element loudspeaker</td><td style="padding:0 5.20px 0 5.20px;"><xref ref-type="sec" rid="sec_5">Clause 5</xref></td><td style="padding:0 5.20px 0 5.20px;"><italic>R</italic>′<sub>45°</sub></td><td style="padding:0 5.20px 0 5.20px;">Preferred method to estimate the apparent sound reduction index of façade elements</td></tr><tr><td style="padding:0 5.20px 0 5.20px;">2</td><td style="padding:0 5.20px 0 5.20px;">Element road traffic</td><td style="padding:0 5.20px 0 5.20px;"><xref ref-type="sec" rid="sec_6">Clause 6</xref></td><td style="padding:0 5.20px 0 5.20px;"><italic>R</italic>′<sub>tr,s</sub></td><td style="padding:0 5.20px 0 5.20px;">Alternative to method No.1 when road traffic noise of sufficient level is available</td></tr><tr><td style="padding:0 5.20px 0 5.20px;">3</td><td style="padding:0 5.20px 0 5.20px;">Element railway traffic</td><td style="padding:0 5.20px 0 5.20px;"><xref ref-type="app" rid="sec_D">Annex D</xref><break/>(informative)</td><td style="padding:0 5.20px 0 5.20px;"><italic>R</italic>′<sub>rt,s</sub></td><td style="padding:0 5.20px 0 5.20px;">Alternative to method No.1 when railway traffic noise of sufficient level is available</td></tr><tr style="border-bottom:solid 2px;"><td style="padding:0 5.20px 0 5.20px;">4</td><td style="padding:0 5.20px 0 5.20px;">Element air traffic</td><td style="padding:0 5.20px 0 5.20px;"><xref ref-type="app" rid="sec_D">Annex D</xref><break/>(informative)</td><td style="padding:0 5.20px 0 5.20px;"><italic>R</italic>′<sub>at,s</sub></td><td style="padding:0 5.20px 0 5.20px;">Alternative to method No.1 when air traffic noise of sufficient level is available</td></tr><tr style="border-top:solid 2px;"><td style="padding:0 5.20px 0 5.20px;"/><td style="padding:0 5.20px 0 5.20px;"><bold>Global</bold></td><td style="padding:0 5.20px 0 5.20px;"/><td style="padding:0 5.20px 0 5.20px;"/><td style="padding:0 5.20px 0 5.20px;"/></tr><tr><td style="padding:0 5.20px 0 5.20px;">5</td><td style="padding:0 5.20px 0 5.20px;">Global loudspeaker</td><td style="padding:0 5.20px 0 5.20px;"><xref ref-type="sec" rid="sec_5">Clause 5</xref></td><td style="padding:0 5.20px 0 5.20px;"><italic>D</italic><sub>ls,2m,n<italic>T</italic></sub><break/><italic>D</italic><sub>ls,2m,n</sub></td><td style="padding:0 5.20px 0 5.20px;">Alternative to methods Nos. 6, 7 and 8</td></tr><tr><td style="padding:0 5.20px 0 5.20px;">6</td><td style="padding:0 5.20px 0 5.20px;">Global road traffic</td><td style="padding:0 5.20px 0 5.20px;"><xref ref-type="sec" rid="sec_6">Clause 6</xref></td><td style="padding:0 5.20px 0 5.20px;"><italic>D</italic><sub>tr,2m,n<italic>T</italic></sub><break/><italic>D</italic><sub>tr,2m,n</sub></td><td style="padding:0 5.20px 0 5.20px;">Preferred method to estimate the global sound insulation of a façade exposed to road traffic noise</td></tr><tr><td style="padding:0 5.20px 0 5.20px;">7</td><td style="padding:0 5.20px 0 5.20px;">Global railway traffic</td><td style="padding:0 5.20px 0 5.20px;"><xref ref-type="app" rid="sec_D">Annex D</xref><break/>(informative)</td><td style="padding:0 5.20px 0 5.20px;"><italic>D</italic><sub>rt,2m,n<italic>T</italic></sub><break/><italic>D</italic><sub>rt,2m,n</sub></td><td style="padding:0 5.20px 0 5.20px;">Preferred method to estimate the global sound insulation of a façade exposed to railway traffic noise</td></tr><tr><td style="padding:0 5.20px 0 5.20px;">8</td><td style="padding:0 5.20px 0 5.20px;">Global air traffic</td><td style="padding:0 5.20px 0 5.20px;"><xref ref-type="app" rid="sec_D">Annex D</xref><break/>(informative)</td><td style="padding:0 5.20px 0 5.20px;"><italic>D</italic><sub>at,2m,n<italic>T</italic></sub><break/><italic>D</italic><sub>at,2m,n</sub></td><td style="padding:0 5.20px 0 5.20px;">Preferred method to estimate the global sound insulation of a façade exposed to air traffic noise</td></tr></tbody></table></table-wrap>
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