SN EN ISO 3747 : 2011

Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Test methodology
      4.1 General
      4.2 Accuracy
5 Measurement uncertainty
6 Instrumentation
      6.1 Instrumentation system
      6.2 Calibration
7 Operating conditions of the source under test
8 Preliminary survey
      8.1 Background noise
      8.2 Characterization of the source under test
9 Positions of the reference sound source
      9.1 One position
      9.2 More than one position
10 Measurement procedure
      10.1 Selection of microphone positions
      10.2 Measurements
      10.3 Correction for background noise
      10.4 Evaluation of the measurement uncertainty
11 Calculation of sound power levels
      11.1 One RSS position
      11.2 Several RSS positions
      11.3 A-weighted sound power level
12 Information to be recorded
13 Information to be reported
Annex A (normative) Evaluation of DLf and of the measurement
                    uncertainty
Annex B (informative) Recommendations for the location of
                      the reference sound source and the
                      microphones, if only one RSS position
                      is used
Bibliography

Specifies a procedure to determine sound power levels of sound sources in situ, especially if non-movable. A comparison method is used, with all measurements carried out in octave bands. Measurement uncertainty depends on the test environment. This is evaluated by comparing with an indicator describing the spatial sound distribution. The accuracy will either be that of an engineering method or a survey method. Primarily applies to sources which radiate broad-band noise. May also be used for sources radiating narrow-band noise or discrete tones, although the measurement uncertainty might become larger than stated.