AS 1217.4-1985

1 - AS 1217.4-1985 ACOUSTICS - DETERMINATION OF SOUND POWER LEVELS OF NOISE SOURCES - ENGINEERING METHODS FOR SPECIAL REVERBERAT
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 Types of noise.
9 - 1.2.2 Size of source.
9 - 1.3 REFERENCED DOCUMENTS.
9 - 1.4 MEASUREMENT UNCERTAINTY.
9 - 1.5 DEFINITIONS.
9 - 1.5.1 Special reverberation test room
9 - 1.5.2 Reverberant sound field
9 - 1.5.3 Mean-square pressure
10 - 1.5.4 Sound pressure level
10 - 1.5.5 Sound power level
10 - 1.5.6 Frequency range of interest
10 - 1.5.7 Direct method
10 - 1.5.8 Comparison method
10 - 1.5.9 Volume of source under test
11 - SECTION 2. TEST ROOM REQUIREMENTS
11 - 2.1 GENERAL.
11 - 2.2 ROOM VOLUME.
11 - 2.3 REVERBERATION TIME OF TEST ROOM.
11 - 2.4 SURFACE TREATMENT.
11 - 2.5 CRITERION FOR BACKGROUND NOISE.
11 - 2.6 CRITERIA FOR TEMPERATURE AND HUMIDITY.
11 - 2.7 TEST OF ROOM SUITABILITY.
12 - SECTION 3. INSTRUMENTATION
12 - 3.1 GENERAL.
12 - 3.2 THE MICROPHONE AND ITS ASSOCIATED CABLE.
12 - 3.3 AMPLIFIER AND WEIGHTING NETWORK.
12 - 3.4 OCTAVE BAND FILTERS.
12 - 3.5 SQUARING AND AVERAGING CIRCUITS AND INDICATING DEVICE.
12 - 3.6 FREQUENCY RESPONSE OF THE INSTRUMENTATION SYSTEM.
12 - 3.7 CALIBRATION.
13 - SECTION 4. INSTALLATION AND OPERATION OF SOURCE
13 - 4.1 GENERAL.
13 - 4.2 SOURCE POSITION.
13 - 4.3 SOURCE MOUNTING.
13 - 4.4 AUXILIARY EQUIPMENT.
13 - 4. 5 OPERATION OF SOURCE DURING TEST.
14 - SECTION 5. MEASUREMENT OF NOISE EMITTED BY SOURCE IN THE TEST ROOM
14 - 5.1 GENERAL.
14 - 5.2 PERIOD OF OBSERVATION.
14 - 5.3 MICROPHONE POSITIONS.
14 - 5.4 NUMBER OF MICROPHONE AND SOURCE POSITIONS.
15 - 5.5 CRITERIA FOR THE PRESENCE OF SPECTRAL IRREGULARITIES.
15 - 5.6 AVERAGING TECHNIQUE WITH MOVING MICROPHONE.
15 - 5.6.1 General.
15 - 5.6.2 Path length for continuous averaging.
15 - 5.6.3 Position of path within test room.
15 - 5.6.4 Speed of traverse.
15 - 5.7 ARRAY OF FIXED MICROPHONES.
15 - 5.8 CORRECTION FOR BACKGROUND SOUND PRESSURE LEVELS.
16 - SECTION 6. CALCULATION OF SOUND POWER LEVELS
16 - 6.1 CALCULATION PROCEDURE FOR THE MEAN BAND PRESSURE LEVELS.
16 - 6.2 DIRECT METHOD FOR DETERMINATION OF SOUND POWER LEVELS.
16 - 6.3 COMPARISON METHOD FOR DETERMINATION OF BAND POWER LEVELS.
17 - SECTION 7. INFORMATION TO BE RECORDED
17 - 7.1 SOUND SOURCE UNDER TEST.
17 - 7.2 ACOUSTIC ENVIRONMENT.
17 - 7.3 INSTRUMENTATION.
17 - 7.4 ACOUSTICAL DATA.
17 - 7.5 INFORMATION TO BE REPORTED.
18 - APPENDIX A - GUIDELINES FOR THE DESIGN OF SPECIAL REVERBERATION TEST ROOMS
18 - A1 GENERAL.
18 - A2 SIZE AND SHAPE OF TEST ROOM.
18 - A3 ABSORPTION OF TEST ROOM.
20 - A4 SOUND ISOLATION.
20 - A5 EXAMPLE OF A PROCEDURE FOR DETERMINATION OF THE NOMINAL REVERBERATION TIME TN OF A ROOM.
22 - APPENIDX B - EXAMPLES OF SUITABLE INSTRUMENTATION SYSTEMS
22 - B1 GENERAL.
22 - B2 RC- SMOOTHING, SOUND LEVEL METER.
22 - B3 ANALOGUE INTEGRATORS.
22 - B4 DIGITAL SYSTEMS.
22 - B5 LEVEL RECORDERS.

Sets out an engineering method for determining the approximate sound power level of small noise sources, which is applicable only to noise sources for which one or more identifiable and reproducible modes of operation exists. Applies to small noise sources producing steady noise within a specified frequency range.

This standard sets out relatively simple engineering methods for determining the approximate sound power levels of small noise sources. The measurements are carried out when the source is installed in a specially designed room having a prescribed reverberation time over the frequency range of interest. The results of the measurements are given in terms of the A-weighted and/or octave-band power levels of the source.NOTE: Precision methods for the determination of octave band and one-third octave band power levels of small noise sources are set out in AS 1217.1, AS 1217.2 and AS 1217.6.FIELD OF