ISO INTERNATIONAL STANDARD 3743-2 Second edition 2018-02 Acoustics Determination of sound power levels of noise sources using sound pressure Engineering methods for small, movable sources in reverberant fields - Part 2: Methods for special reverberation test rooms Acoustique-Détermination des niveauxdepuissance acoustique émis par les sources de bruita partir de la pression acoustique Méthodes d'expertiseen champréverbére applicables auxpetites sources transportables- Partie2:Méthodes en salled'essai réverberantespeciale Reference number IS0 3743-2:2018(E) ISO @ IS0 2018 IS03743-2:2018(E) COPYRIGHTPROTECTEDDOCUMENT IS02018 All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting below or Iso's member body in the country of the requester. ISO copyright office CP 401 : Ch. de Blandonnet 8 CH-1214 Vernier, Geneva Phone:+4122749 0111 Fax: +41 22 749 09 47 Email: [email protected] Website: www.iso.org Published in Switzerland ii @ IS0 2018 - All rights reserved IS03743-2:2018(E) Contents Page Foreword ..V Introduction. ..vi 1 Scope. 2 Normative references 3 Terms and definitions 4 Principle ..2 5 Noise source .2 6 Requirements forspecialreverberationtestroom .2 6.1 General .2 Volume of test room. .2 6.2 6.3 Reverberation time oftestroom 3 6.4 .3 Surface treatment.. 6.5 Criterion for background noise. .3 .4 6.6 Criteriafortemperatureand humidity 6.7 Evaluation of suitability of test room. 4 7 Instrumentation. .5 7.1 ..5 General 7.2 Microphone and its associated cable .5 7.3 Amplifier andweighting network 7.4 Octave-band filters .6 7.5 Squaring and averaging circuits and indicating device .6 7.6 Frequency response of the instrumentation system .6 7.7 Calibration .6 8 Installation and operation of source under test .6 8.1 General .6 8.2 Source location. .6 8.3 Source mounting 8.4 Auxiliary equipment. .7 8.5 Operation of source during thetest ..8 9 Measurementsin testroom 9.1 General .8 9.2 Period ofobservation 9.3 Microphonepositions .8 9.4 Number of microphones and sourcepositions 9.5 Criteriafor the presence of spectral irregularities .10 9.6 Averaging technique with moving microphones. ..10 9.6.1 General. ..10 9.6.2 Path length for continuous averaging .10 9.6.3 Location of pathwithintest room ..10 9.6.4 Speed of traverse .10 9.7 Array offixedmicrophones. ..11 9.8 Correctionforbackground sound pressurelevels .11 10 Calculation of sound power levels .11 10.1 Calculation ofmean band pressurelevels ..11 10.2 Direct method for determining sound power levels ..12 10.3 Comparison method for determining band power levels ..12 10.4 A-weighted sound power levels determined bythe comparison method .13 11 Measurement uncertainty ..13 11.1 Methodology ..13 11.2 Determination of oomc .14 @ IS0 2018 - All rights reserved iii