AS 1217.6-1985

1 - AS 1217.6-1985 ACOUSTICS - DETERMINATION OF SOUND POWER LEVELS OF NOISE SOURCES - PRECISION METHODS FOR ANECHOIC AND HEMI-AN
4 - PREFACE
5 - CONTENTS
7 - FOREWORD
8 - SYNOPSIS
9 - SECTION 1. SCOPE AND GENERAL
9 - 1.1 SCOPE.
9 - 1.2 FIELD OF APPLICATION.
9 - 1.2.1 General.
9 - 1.2.2 Types of noise.
9 - 1.2.3 Size of source.
9 - 1.3 REFERENCED DOCUMENTS.
9 - 1.4 MEASUREMENT UNCERTAINTY.
10 - 1.5 DEFINITIONS.
10 - 1.5.1 Free sound field
10 - 1.5.2 Free field over a reflecting plane
10 - 1.5.3 Anechoic room
10 - 1.5.4 Hemi-anechoic room
10 - 1.5.5 Surface sound pressure
10 - 1.5.6 Surface sound pressure level
10 - 1.5.7 Sound power level
10 - 1.5.8 Frequency range of interest
10 - 1.5.9 Measurement surface
10 - 1.5.10 Far field
10 - 1.5.11 Near field
10 - 1.5.12 Volume of source under test
11 - SECTION 2. TEST ROOM REQUIREMENTS
11 - 2.1 GENERAL.
11 - 2.1.1 Size.
11 - 2.1.2 Criterion for room adequacy.
11 - 2.1.3 Criterion for background noise.
11 - 2.2 ROOM VOLUME.
11 - 2.3 CRITERIA FOR TEMPERATURE AND HUMIDITY.
11 - 2.4 CRITERIA FOR THE REFLECTING PLANE.
12 - SECTION 3. INSTRUMENTATION
12 - 3.1 GENERAL.
12 - 3.2 THE MICROPHONE AND ITS ASSOCIATED CABLE
12 - 3.3 FREQUENCY RESPONSE OF THE INSTRUMENTATION SYSTEM.
12 - 3.4 WEIGHTING NETWORK, FREQUENCY ANALYSER.
12 - 3.5 CALIBRATION.
13 - SECTION 4. INSTALLATION AND OPERATION OF SOURCE
13 - 4.1 GENERAL.
13 - 4.2 INSTALLATION OF SOURCE.
13 - 4.3 METHOD OF MOUNTING.
13 - 4.4 CHOICE OF MOUNTING METHOD.
13 - 4.5 AUXILIARY EQUIPMENT.
13 - 4.6 OPERATION OF SOURCE DURING TEST.
14 - SECTION 5. DETERMINATION OF MEAN-SQUARE PRESSURE
14 - 5.1 GENERAL.
14 - 5.2 MEASUREMENT SURFACE.
14 - 5.2.1 Radius of test sphere.
14 - 5.2.2 Radius of test hemisphere.
14 - 5.3 MICROPHONE POSITIONS.
14 - 5.3.1 General.
14 - 5.3.2 Fixed microphone positions.
14 - 5.3.3 Coaxial circular paths in parallel planes.
15 - 5.3.4 Meridional arc traverses.
15 - 5.4 CONDITIONS OF MEASUREMENT.
15 - 5.4.1 General.
15 - 5.4.2 Measurement with sound level meter.
15 - 5.4.3 Measurementwith RC-smoothing or integrating systems.
15 - 5.5 OBSERVATIONS TO BE OBTAINED.
15 - 5.6 CORRECTION FOR BACKGROUND SOUND PRESSURE LEVELS.
16 - 5.7 CALCULATION OF SURFACE SOUND PRESSURE LEVEL.
16 - 5.7.1 General.
16 - 5.7.2 Fixed microphone positions.
16 - 5.7.3 Circular microphone traverses.
16 - 5.7.4 Traverses along circular arcs.
17 - SECTION 6. CALCULATION OF SOUND POWER LEVEL
17 - 6.1 FREE FIELD.
17 - 6.2 FREE FIELD OVER A REFLECTING PLANE.
17 - 6.3 WEIGHTED SOUND POWER LEVEL AND BAND SOUND POWER LEVELS.
18 - SECTION 7. INFORMATION TO BE RECORDED AND REPORTED
18 - 7.1 INFORMATION TO BE RECORDED.
18 - 7.1.1 General.
18 - 7.1.2 Sound Source Under Test.
18 - 7.1.3 Acoustic Environment.
18 - 7.1.4 Acoustical Data.
18 - 7.1.5 Instrumentation.
18 - 7.2 INFORMATION TO BE REPORTED.
19 - APPENDIX A - TEST ROOM QUALIFICATION PROCEDURES
19 - A1 GENERAL.
19 - A2 PROPERTIES OF REFLECTING PLANE.
19 - A2.1 General.
19 - A2.2 Shape and size.
19 - A2.3 Absorption coefficient.
19 - A3 SOUND PRESSURE DECREASE TEST.
19 - A3.1 Instrumentation.
19 - A3.2 Installation of test source and microphone.
19 - A3.3 Test procedure.
20 - A3.4 Qualification requirements.
21 - APPENDIX B - RECOMMENDED ARRAY OF MICROPHONE POSITIONS IN A FREE FIELD
23 - APPENDIX C- BASIC ARRAY OF MICROPHONE POSITIONS IN A FREE FIELD OVER A REFLECTING PLANE
25 - APPENDIX D - COAXIAL CIRCULAR PATHS IN PARALLEL PLANES FOR MICROPHONE TRAVERSES IN A FREE FIELD OVER A REFLECTING PLANE
26 - APPENDIX E - CALCULATION OF DIRECTIVITY INDEX AND DIRECTIVITY FACTOR
26 - E1 FREE FIELD.
26 - E2 FREE FIELD OVER A REFLECTING PLANE.
27 - APPENDIX F - SYSTEM FOR MICROPHONE TRAVERSES ALONG MERIDIONAL PATHS IN A FREE FIELD
28 - APPENDIX G - GUIDELINES FOR THE DESIGN OF TEST ROOMS
28 - G1 GENERAL.
28 - G2 VOLUME OF TEST ROOM.
28 - G3 SHAPE OF TEST ROOM.
28 - G4 ABSORPTION OF TEST ROOM.
28 - G5 ABSORPTIVE TREATMENT.
28 - G6 UNWANTED REFLECTIONS.
28 - G7 SUSPENDED FLOOR CONSTRUCTION.
28 - G8 BACKGROUND NOISE.
28 - G9 AIR ABSORPTION.
29 - APPENIDX H - EXAMPLES OF SUITABLE INSTRUMENTATION SYSTEMS
29 - H1 GENERAL.
29 - H2 RC-SMOOTHING, SOUND LEVEL METER.
29 - H3 ANALOGUE INTEGRATORS.
29 - H4 DIGITAL SYSTEMS.
29 - H5 LEVEL RECORDERS.
30 - APPENIDX J - GUIDELINES FOR THE DETECTION OF IMPULSIVE NOISE

Sets out two laboratory methods for determining the sound power radiated by a device, machine component or subassembly using a laboratory anechoic room having prescribed acoustical characteristics. Applies to sources which produce sound that is uniformly distributed in frequency over the frequency range of interest and is relatively steady for at least 30 s. Applies primarily to small sound sources, i.e. sources whose volumes are preferably less than 0.5 percent of the volume of the test room used for the measurements.

This standard sets out in detail two laboratory methods for determining the sound power radiated by a device, machine, component or subassembly using a laboratory anechoic room having prescribedacoustical characteristics. While other methods could be used to measure the noise emitted by machinery and equipment, the methods specified in this standard are particularly useful for rating the sound output of sources which produce steady noise and for which directivity information on the source may be desired.The methods specified in this standard yield physical data that may be used for the following purposes:(a) Rating apparatus according to its sound power output.(b) Establishing sound control measures.(c) Predicting the sound pressure levels produced by a device in a given enclosure or environment. Techniques for utilizing the physical data for these special purposes are not included in this standard. The determination of the sound power radiated by a sound source in a completely free field or in a free field above a reflecting plane is based on the premise that the reverberant field produced by the source is negligible and that the total radiated power is obtained from the mean square sound pressure averaged in time and in space over a hypothetical sphere or hemisphere surrounding the source. The radius of the sphere or hemisphere is chosen so that its surface is in the far radiation field of the source.