AS 1081.1-1990

1 - AS 1081.1-1990 ACOUSTICS - MEASUREMENT OF AIRBORNE NOISE EMITTED BY ROTATING ELECTRICAL MACHINERY - ENGINEERING METHOD FOR FR
4 - PREFACE
5 - CONTENTS
6 - 0 Introduction
6 - 1 Scope and field of application
6 - 1.1 General
6 - 1.2 Measurement uncertainty
6 - 2 References
7 - 3 Definitions
7 - 3.1 free field:
7 - 3.2 free field over a reflecting plane:
7 - 3.3 anechoic room:
7 - 3.4 semi-anechoic room:
7 - 3.5 sound pressure level
7 - 3.6 surface sound pressure:
7 - 3.7 surface sound pressure level
7 - 3.8 sound power level
7 - 3.9 frequency range of interest:
7 - 3.10 measurement surface:
7 - 3.11 reference box:
7 - 3.12 measurement distance:
7 - 3.13 background noise:
8 - 4 Acoustic environment
8 - 4.1 General
8 - 4.2 Criteria for adequacy of the test environment
8 - 4.3 Criterion for background noise
8 - 4.4 Wind
8 - 5 Instrumentation
8 - 5.1 General
8 - 5.2 The microphone and its associated cable
8 - 5.3 Frequency response of the instrumentation system
9 - 5.4 Weighting network and frequency analyser
9 - 5.5 Calibration
9 - 6 Installation and operation of the machine
9 - 6.1 Machine mounting
9 - 6.1.1 Resilient mounting
9 - 6.1.2 Rigid mounting
9 - 6.2 Operation of machine during test
9 - 6.3 Auxiliary equipment and coupled machines
9 - 7 Sound pressure levels on the measurement surface
9 - 7.1 Reference box and measurement surfaces
10 - 7.2 Microphone array
10 - 7.2.1 Complete measurement position array
10 - 7.2.2 Simplified measurement position array
10 - 7.3 Conditions of measurement
10 - 7.3.1 General
10 - 7.3.2 Measurements with a sound level meter
10 - 7.3.3 Measurements with RC- smoothing or integration systems
13 - 8 Calculation of surface sound pressure level and sound power level
13 - 8.1 Corrections for background noise
13 - 8.2 Calculation of sound pressure level averaged over the measurement surface
13 - 8.3 Calculation of surface sound pressure level
13 - 8.4 Calculation of sound power level
13 - 9 Information to be recorded
13 - 9.1 Machine under test
13 - 9.2 Acoustic environment
14 - 9.3 Instrumentation
14 - 9.4 Acoustical data
14 - 10 Information to be reported
15 - Annex A - Qualification Procedures for the acoustic environment
15 - A.1 General
15 - A.2 Environmental conditions
15 - A.2.1 Properties of reflecting plane
15 - A.2.2 Reflecting objects
15 - A.2.3 Precautions for outdoor measurements
16 - A.3 Absolute comparison test to determine
16 - A.3.1 Procedure
16 - A.3.2 Locations of reference sound source in test environment
16 - A.3.3 Qualification requirements
16 - A.4 Reverberation test to determine K
16 - A.4.1 Test procedure
16 - A.4.2 Qualification requirements
18 - Annex B - Procedures for calculating A-weighted sound power level from octave or one-third octave band power levels
19 - Annex C - Method for estimating the difference in noise level between no-load and on-load operations
19 - C.1 General
19 - C.2 Installation and operation of machines
19 - C.2.1 Machine mounting
19 - C.2.2 Operation of machine during test
19 - C.3 Measurement array
19 - C.4 Measurement of sound pressure levels
20 - C.5 Estimation of differences in level of the noise between no-load and on-load operations
20 - C.6 Information to be recorded
20 - C.7 Information to be reported

Specifies an engineering method for measuring the sound pressure levels on a rectangular parallel piped surface enveloping the machine and for calculating sound power level produced by the machine. Applies to the rotating electrical machines, such as motors, and generators (d.c. and a.c.) without any limitations on the output voltage but with the limit of the linear dimensions not to exceed 15 m. Identical with and reproduced from ISO 1680-1.

This part of ISO 1680 specifies, in accordance with ISO 2204, an engineering method (grade 2) for measuring the sound pressure levels on a rectangular parallelepiped surface enveloping the machine and for calculating the sound power level produced by the machine. It outlines the procedures which may be used to evaluate the test environment and specifies the characteristics of suitable measuring instruments. A method is given for determining the A-weighted sound power level and, if required, octave or one-third octave band sound power levels of the machine from the mean of the sound pressure levels measured on the rectangular parallelepiped surface.This part of ISO 1680 applies to the measurement of airborne noise from rotating electrical machines, such as motors and generators (d.c. and a.c. machines) without any limitation on the output or voltage, when fitted with their normal auxiliaries. It applies to rotating electrical machines with any linear dimension (length, width or height) not exceeding 15 m.This part of ISO 1680 applies to measurements carried out in environmental conditions that meet the criteria given in clause 4 and annex A (environmental correction K 2 dB, correction for background noise 1 dB). If these criteria are not met, standard deviations of the test results may be greater than those given in table 1, i.e. the engineering grade of accuracy may not be achieved. The method given in ISO 1680/2 shall then be used, which will result in A-weighted sound power levels of lower accuracy. In this case, no reference shall be made to this part of ISO 1680.

First published in part as AS 1081-1975. Revised and redesignated AS 1081.1-1990.