AS 1217.7-1985

1 - AS 1217.7- 1985 ACOUSTICS - DETERMINATION OF SOUND POWER LEVELS OF NOISE SOURCES - SURVEY METHOD
4 - PREFACE
4 - CONTENTS
5 - FOREWORD
6 - SYNOPSIS
7 - SECTION 1. SCOPE AND GENERAL
7 - 1.1 SCOPE.
7 - 1.2 FIELD OF APPLICATION.
7 - 1.2.1 General.
7 - 1.2.2 Types of noise.
7 - 1.2.3 Size of source.
7 - 1.3 REFERENCED DOCUMENTS.
8 - 1.4 MEASUREMENT UNCERTAINTY.
8 - 1.5 DEFINITIONS.
8 - 1.5.1 Sound pressure level
8 - 1.5.2 A-weighted surface sound pressure level Lpa in decibels
8 - 1.5.3 Sound power level
8 - 1.5.4 Measurement surface
8 - 1.5.5 Reference surface
8 - 1.5.6 Measurement distance
8 - 1.5.7 Background noise
9 - SECTION 2. ACOUSTIC ENVIRONMENT
9 - 2.1 CRITERIA FOR ADEQUACY OF THE TEST ENVIRONMENT.
9 - 2.2 CRITERION FOR BACKGROUND NOISE.
9 - 2.3 WIND.
9 - SECTION 3. INSTRUMENTATION
9 - 3.1 GENERAL.
9 - 3.2 CALIBRATION.
9 - SECTION 4. INSTALLATION AND OPERATION OF SOURCE
9 - 4.1 GENERAL.
9 - 4.2 AUXILIARY EQUIPMENT.
9 - 4.3 OPERATION OF SOURCE DURING TESTS.
10 - SECTION 5. MEASUREMENT OF WEIGHTED SOUND PRESSURE LEVELS
10 - 5.1 MEASUREMENT SURFACE.
10 - 5.2 REFERENCE SURFACE.
10 - 5.3 MEASUREMENTS ON HEMISPHERICAL MEASUREMENT SURFACE.
10 - 5.3.1 Microphone positions.
10 - 5.3.2 Preliminary measurements.
10 - 5.3.3 Measurements on hemispherical array.
10 - 5.4 MEASUREMENTS ON RECTANGULAR MEASUREMENT SURFACE.
10 - 5.4.1 Microphone positions.
13 - 5.4.2 Preliminary measurements.
13 - 5.4.3 Number of microphone positions.
13 - 5.4.4 Measurements on rectangular array.
13 - 5.5 CORRECTIONS FOR BACKGROUNDNOISE.
14 - SECTION 6. CALCULATION OF SURFACE SOUND PRESSURE LEVEL AND SOUND POWER LEVEL
14 - 6.1 CALCULATION OF SURFACE SOUND PRESSURE LEVEL.
14 - 6.2 CALCULATION OF SOUND POWER LEVEL.
15 - SECTION 7. INFORMATION TO BE RECORDED AND REPORTED
15 - 7.1 INFORMATION TO BE RECORDED.
15 - 7.1.1 General.
15 - 7.1.2 Sound source under test.
15 - 7.1.3 Acoustic environment.
15 - 7.1.4 Instrumentation.
15 - 7.1.5 Acoustical data.
15 - 7.2 INFORMATION TO BE REPORTED.
16 - APPENDIX A - TEST ENVIRONMENT QUALIFICATION PROCEDURE
16 - A1 GENERAL.
16 - A2 ENVIRONMENTAL CONDITIONS.
16 - A2.1 Reflecting planes.
16 - A2.2 Reflecting objects.
16 - A2.3 Precautions for outdoor measurements.
16 - A3 QUALIFICATIONPROCEDURE AND REQUIREMENTSFOR TESTROOMS.
16 - A3.1 Test procedures.
18 - A3.2 Qualification requirements for test rooms.
18 - A4 QUALIFICATION REQUIREMENTS FOR OUTDOOR SPACES.
18 - A5 ALTERNATIVE TEST PROCEDURE.

Sets out a survey method for determining the weighted sound power level of a device or a machine. The method should not be used when it is feasible to use a more precise method, e.g. where a laboratory hemi-anechoic room is available for the measurements. The method requires that the background noise be at least 3 dB lower than the noise produced by the source.

This standard sets out a survey method for determining the weighted sound power level of a device or machine. The sound power level of the source is calculated from the measured values of the weighted sound pressure levels at prescribed microphone positions. The method is particularly useful for rating the sound output of a source that produces steady noise (as defined in AS 1633) and cannot be moved from its position to a special test environment.The method requires measurement of the A-weighted sound pressure level at four or more microphone positions on a hypothetical measurement surface which envelops the source. One of two alternative measurement surfaces may be selected, either a hemisphere or a rectangular parallelepiped. The hemispherical surface is best suited for measurement of the noise emitted by small sources as well as that emitted by larger sources which are approximately cubical in shape. The rectangular parallelepiped is best suited for long or tall sound sources as well as for those situations in which measurement must be carried out close to the source. This may occur when use of the hemispherical surface leads to microphone positions that are not sufficiently far away from reflecting surfaces, when measured levels with the source in operation are close to the background noise levels, or when other unfavourable environmental conditions are present. In general, the hemispherical surface is preferred when the measuring distance is large compared with the dimensions of the source and the rectangular parallelepiped is preferred for close-in measurements.The method yields physical data that may be useful for-(a) comparing machines which are similar in size and kind; or (b) rating apparatus in terms of its overall weighted sound power output.This method should not be used when it is feasible to use a more precise method, e.g. when a laboratory hemi-anechoic room is available for the measurements. The method requires that the background noise be at least 3 dB lower than the noise produced by the source. Appendix A gives a procedure for qualifying the acoustic environment for the purposes of measurements made according to the requirements of this standard. If the test environment does not comply with the requirements of Appendix A, the method is not to be used for determining the sound power level of a source.The method permits the determination of the A-weighted sound power level of a noise source. If additional information is required, e.g. the sound power levels in frequency bands (see AS 1217.4) should be used.