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AS 5333.2:2019
$177.61
Acoustics — Determination of sound power levels of noise sources using sound pressure — Engineering methods for small, movable sources in reverberant fields, Part 2: Methods for special reverberation test rooms
The objective of this Standard is to specify a relatively simple engineering method for determining the sound power levels of small, movable noise sources.
Table of contents
Header
About this publication
Preface
Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Principle
5 Noise source
6 Requirements for special reverberation test room
6.1 General
6.2 Volume of test room
6.3 Reverberation time of test room
6.4 Surface treatment
6.5 Criterion for background noise
6.6 Criteria for temperature and humidity
6.7 Evaluation of suitability of test room
7 Instrumentation
7.1 General
7.2 Microphone and its associated cable
7.3 Amplifier and weighting network
7.4 Octave-band filters
7.5 Squaring and averaging circuits and indicating device
7.6 Frequency response of the instrumentation system
7.7 Calibration
8 Installation and operation of source under test
8.1 General
8.2 Source location
8.3 Source mounting
8.4 Auxiliary equipment
8.5 Operation of source during the test
9 Measurements in test room
9.1 General
9.2 Period of observation
9.3 Microphone positions
9.4 Number of microphones and source positions
9.5 Criteria for the presence of spectral irregularities
9.6 Averaging technique with moving microphones
9.6.1 General
9.6.2 Path length for continuous averaging
9.6.3 Location of path within test room
9.6.4 Speed of traverse
9.7 Array of fixed microphones
9.8 Correction for background sound pressure levels
10 Calculation of sound power levels
10.1 Calculation of mean band pressure levels
10.2 Direct method for determining sound power levels
10.3 Comparison method for determining band power levels
10.4 A-weighted sound power levels determined by the comparison method
11 Measurement uncertainty
11.1 Methodology
11.2 Determination of σomc
11.3 Determination of σR0
11.3.1 General
11.3.2 Round robin test
11.3.3 Modelling approach for σR0
11.4 Typical upper bound values of σR0
11.5 Total standard deviation σtot and expanded uncertainty U
12 Information to be recorded
12.1 General
12.2 Sound source under test
12.3 Acoustical environment
12.4 Instrumentation
12.5 Acoustical data
13 Information to be reported
Annex A
A.1 Characteristics of reference sound source
A.1.1
A.1.2
A.1.3
A.1.4
A.1.5
A.1.6
A.2 Calibration of reference sound source
Annex B
B.1 General
B.2 Size and shape of test room
B.3 Absorption of test room
B.4 Sound insulation
B.5 Example of determination of the nominal reverberation time of a room
Annex C
C.1 General
C.2 RC-smoothing, sound level meter
C.3 Analogue integrators
C.4 Digital systems
C.5 Level recorders
Annex D
D.1 General
D.2 Considerations on the total standard deviation σtot
D.3 Considerations on σomc
D.4 Considerations on σR0
D.4.1 General
D.4.2 Contributions to the uncertainty σR0
D.4.2.1 General
D.4.2.2 Measurement method, δmethod
D.4.2.3 Sound pressure level repeatability, L’p¯
D.4.2.4 Background noise correction, K1
D.4.2.5 Meteorological correction, C2
D.4.2.6 Sound level meter, δslm
D.4.2.7 Sampling, δmic
D.4.2.8 Temperature, δθ
D.4.2.9 Humidity, δH
D.4.2.10 Room volume, V
D.4.2.11 Reverberation time, Tnom
D.4.2.12 Typical value for direct method, σR0
D.5 Combined standard uncertainty
D.6 Measurement uncertainty based on reproducibility data
