AS 1217.5-1985

1 - AS 1217.5-1985 ACOUSTICS - DETERMINATION OF SOUND POWER LEVELS OF NOISE SOURCES - ENGINEERING METHODS FOR FREE-FIELD CONDITI
4 - PREFACE
5 - CONTENTS
7 - FOREWORD
7 - SYNOPSIS
9 - SECTION 1. SCOPE AND GENERAL
9 - 1.1 SCOPE.
9 - 1.2 FIELD OF APPLICATION.
9 - 1.2.1 Types of noise.
9 - 1.2.2 Size of source.
9 - 1.3 REFERENCED DOCUMENTS.
9 - 1.4 MEASUREMENTUNCERTAINTY.
10 - 1.5 DEFINITIONS.
10 - 1.5.1 Free-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 Reference box
10 - 1.5.11 Measurement distance
10 - SECTION 2 ACOUSTIC ENVIRONMENT
10 - 2.1 GENERAL.
10 - 2.2 CRITERIA FOR ADEQUACY OF THE TEST ENVIRONMENT.
10 - 2.3 CRITERION FOR BACKGROUND NOISE.
11 - SECTION 3. INSTRUMENTATION
11 - 3.1 GENERAL.
11 - 3.2 THE MICROPHONE AND ITS ASSOCIATED CABLE.
11 - 3.3 FREQUENCY RESPONSE OF THE INSTRUMENTATION SYSTEM.
11 - 3.4 WEIGHTING NETWORK, FREQUENCY ANALYSER.
11 - 3.5 CALIBRATION.
12 - SECTION 4. INSTALLATION AND OPERATION OF SOURCE
12 - 4.1 GENERAL.
12 - 4.2 SOURCE POSITION.
12 - 4.3 SOURCE MOUNTING.
12 - 4.4 AUXILIARY EQUIPMENT.
12 - 4.5 OPERATION OF SOURCE DURING TEST.
13 - SECTION 5. SOUND PRESSURE LEVELS O N MEASUREMENT SURFACE
13 - 5.1 MEASUREMENT SURFACE.
13 - 5.1.1 Reference surface and measurement surface.
13 - 5.1.2 Coordinate system and definition of distance do.
13 - 5.1.3 Shape of measurement surface.
13 - 5.1.4 Selection of measurement surface.
13 - 5.1.5 Key microphone positions on the hemispherical measurement surface.
14 - 5.1.6 Key microphone positions on the parallelepiped measurement surface.
14 - 5.1.7 Key microphone positions on the conformal measurement surface.
14 - 5.2 ADDITIONAL MICROPHONE POSITIONS ON MEASUREMENT SURFACE.
14 - 5.2.1 General.
14 - 5.2.2 Positions of additional microphones.
14 - 5.2.3 Sufficiency of number of microphone positions.
14 - 5.2.4 Additional localized microphone positions on measurement surface.
14 - 5.3 REDUCTION OF NUMBER OF MICROPHONE POSITIONS.
15 - 5.4 CONDITIONS OF MEASUREMENT.
15 - 5.4.1 General.
15 - 5.4.2 Measurements with sound level meter.
15 - 5.4.3 Measurements with RC-smoothing or integrating systems.
15 - 5.4.4 Corrections for background noise.
16 - SECTION 6. CALCULATION OF SURFACE SOUND PRESSURE LEVEL, SOUND POWER LEVEL, AND DIRECTIVITY FACTOR
16 - 6.1 CALCULATION OF SOUND PRESSURE LEVEL AVERAGED OVER THE MEASUREMENT SURFACE.
16 - 6.2 CALCULATION OF SURFACE SOUND PRESSURE LEVEL.
16 - 6.3 CALCULATION OF SOUND POWER LEVEL.
16 - 6.4 CALCULATION OF DIRECTIVITY INDEX AND DIRECTIVITY FACTOR.
17 - SECTION 7. INFORMATION TO BE RECORDED
17 - 7.1 GENERAL.
17 - 7.2 SOUND SOURCE UNDER TEST.
17 - 7.3 ACOUSTIC ENVIRONMENT.
17 - 7.4 INSTRUMENTATION.
17 - 7.5 ACOUSTICAL DATA.
17 - 7.6 INFORMATION TO BE REPORTED.
18 - APPENDIX A - QUALIFICATION PROCEDURES FOR THE ACOUSTIC ENVIRONMENT
18 - A1 GENERAL.
18 - A2 ENVIRONMENTAL CONDITIONS.
18 - A2.1 Properties of reflecting plane.
19 - A2.2 Precautions for outdoor measurements.
19 - A3 ABSOLUTE COMPARISON TEST.
19 - A3.1 Procedure.
19 - A3.2 Positions of reference sound source in test environment.
19 - A3.3 Qualification requirements.
19 - A4 REVERBERATION TEST.
19 - A4.1 Test procedure.
20 - A4.2 Qualification requirements.
21 - APPENDIX B - MICROPHONE ARRAY ON THE HEMISPHERE
23 - APPENDIX C - MICROPHONE ARRAY ON THE PARALLELE PIPED MEASURING SURFACE
25 - APPENDIX D - MICROPHONE ARRAY ON THE CONFORMAL MEASUREMENT SURFACE
28 - APPENDIX E - EXAMPLES OF SUITABLE INSTRUMENTATION SYSTEMS
28 - E1 GENERAL.
28 - E2 RC-SMOOTHING, SOUND LEVEL METER.
28 - E3 ANALOGUE INTEGRATORS.
28 - E4 DIGITAL SYSTEMS.
28 - E5 LEVEL RECORDERS.
29 - APPENDIX F - GUIDELINES FOR THE DETECTION OF IMPULSIVE NOISE
30 - APPENDIX G - CALCULATION OF DIRECTIVITY INDEX AND DIRECTIVITY FACTOR USING HEMISPHERICAL MICROPHONE ARRAY

Sets out engineering methods for measuring the sound pressure levels on a measurement surface enveloping the source and for calculating the sound power level produced by the source. Applies to sources which radiate broad-band noise, narrow-band noise, discrete tones and combinations of such components. Specifies procedures which apply to steady noise and to non-steady noise with the exception of an isolated burst of sound energy or a burst train with a repetition rate less than 10 s.

This standard sets out engineering methods for measuring the sound pressure levels on a measurement surface enveloping the source and for calculating the sound power level produced by the source. It gives requirements for the test environment and instrumentation as well as techniques for obtaining the surface sound pressure level from which the A-weighted sound power level of the source and octave or one-third octave band sound power levels are calculated.NOTES:1. This standard is concerned with specification of the basic acoustic requirements for the measurement of noise under free-field conditions over a reflecting plane. It is important that specific test codes for various types of equipment be established and used as the basis for measurements according to this standard. Such test codes will, for each type of equipment, give detailed requirements on mounting, loading and operating conditions for the equipment under test as well as descriptions of the measurement surface, the number of microphone positions, and the measurement distance to be used.2. The use of different measurement surfaces may yield differing estimates of the sound power level of a source. Measurements on a given family of equipment should all be based on the same shape of measurement surface. The test method for a particular type of equipment should give detailed information on the particular measurement surface that is selected.