ISO INTERNATIONAL STANDARD 10494 Second edition 2018-04 Turbines and turbine sets- Measurement of emitted airborne noiseEngineering/survey method Turbines et groupes de turbines-Mesurage du bruit aérien émis- Méthoded'expertiseldecontrole Reference number ISO 10494:2018(E) ISO O ISO 2018 ISO 10494:2018(E) COPYRIGHT PROTECTED DOCUMENT ISO 2018 Allrights reserved.Unless otherwise specified,or required in the context of its implementation,no partofthis publication may be reproduced or utilized otherwise in any form or by any means,electronic or mechanical,including ,photocopying,or posting on the internet or an intranet,without prior writen permission.Permission can be requested from either IsO at the address beloworISO's member body in the country of the requester. ISO copyright office CP 401.Ch.de , Blandonnet 8 8 CH-1214 Vernier,Geneva Phone:+41227490111 Fax:+41227490947 Email:[email protected] Website:wwwiso.org Published in Switzerland i ISO 2018-All rights reserved ISO 10494:2018(E) Contents Page Foreword Introduction 1 Scope 2 Normative references 3 Terms and definitions 4 Acoustic environment 4.1 Criteria of adequacy of the testenvironment 4.2 Criteria for background noise 4.3 4.4 Special measurement methods 5 Instrumentation 6 Installation and operation of turbine set 6.1 General 6.2 Mounting of turbine set 6.3 Operation of turbine set duringtest 6.4 Sound pressure levels on the measurement surface 7 7.1 Reference surface and measurementsurface 7.2 Location and number of microphone positions 7.2.1 General . 7.2.2 Additional microphone positions on measurement surface 10 7.2.3 Surface noise .. 7.3 Conditions of measurement 7.3.1 General 11 7.3.2 Calibration 7.3.3 Measurement of the A-weighted sound pressure level 7.3.4 Measurement of sound pressure spectrum ....... Calculation ofsurface sound pressurelevel and sound power level 8 8.1 Corrections for background noise 12 8.2 Calculation of sound pressure level averaged over the measurement surface 8.3 Calculation of surface time-averaged sound pressure levels 8.4 Calculation of sound power level . 13 8.5 Calculation of directivity index and directivity factor Information to be recorded 9 14 9.1 General 9.2 Noise source under test 9.3 Acoustic environment 14 ........... 9.4 Instrumentation 9.5 Acoustical data 15 9.6 Dateand location 15 Test report 10 .15 AnnexA (normative) Qualification procedures for the acoustic environment 16 AnnexB (normative )Gas turbines ..20 Annex C(normative ) Steam turbines 31 Annex D (informative)Calculation of directivity indexand directivity factorusing a hemispherical microphone array ......... .36 Bibliography 37 @ ISO 2018-All rights reserved ii