Acoustics--Determination of sound power levels and sound energy levels of noise sources using sound pressure--Precision methods for anechoic rooms and hemi-anechoic rooms
1 Scope
1.1 General
This standard specifies the methods for measuring the sound pressure levels on a measurement surface enveloping a noise source (machinery or equipment) in an anechoic room or a hemi-anechoic room. The sound power level (and in case of impulsive or transient noise radiation, the sound energy level) of noise source in frequency bands of width one-third octave or with frequency weighting A applied, is calculated using those measurements, including corrections to allow for any differences between the meteorological conditions at the time and place of the test and those corresponding to a reference characteristic acoustic impedance.
In general, the frequency range of interest is the one-third-octave bands with mid-band frequencies from 100Hz to 10,000Hz. As required, the range is extended or restricted to frequencies beyond or within these limits, to those between which the test room is qualified for the purpose of measurement.
1.2 Types of noise and noise sources
The methods specified in this standard are suitable for all types of noise (steady, non-steady, fluctuating, isolated burst of sound energy, etc.) defined in GB/T 19052.
The noise source under test can be a device, machine, component or sub-assembly. The maximum size of the noise source depends on specified requirements regarding the radius of the hypothetical sphere or hemisphere used as the enveloping measurement surface.
1.3 Test room
The test rooms that are applicable for measurements made in accordance with this standard are an anechoic room or hemi-anechoic room, also called, respectively, a free-field test room or hemi-free-field test room.
1.4 Measurement uncertainty
Information is given on the uncertainty of the sound power levels and sound energy levels determined in accordance with this standard, for measurements made in specified bands of frequency and with frequency weighting A applied. The uncertainty conforms to Accuracy Grade 1 in GB/T 19052-2003.
2 Normative References
The following documents are indispensable for the application of this standard. For dated reference, only the edition cited applies. For undated reference, the latest edition (including any amendments) applies.
GB/T 3785.1-2010 Electroacoustics — Sound Level Meters — Part 1: Specifications(IEC 61672-1:2002, IDT)
GB/T 15173-2010 Electroacoustics — Sound Calibrators (IEC 60942:2003, IDT)
GB/T 19052-2003 Acoustics - Noise Emitted by Machinery and Equipment-Rules for the Drafting and Presentation of A Noise Test Code (ISO 12001:1996, IDT)
ISO 5725 (All Parts) [Accuracy (Trueness and Precision) of Measurement Methods and Results]
SO 9613—1:1993 Acoustics — Attenuation of Sound during Propagation Outdoors — Part 1: Calculation of the Absorption of Sound by the Atmosphere)
IEC 61183:1994 Electroacoustics — Random— Incidence and Diffuse — Field Calibration of Sound Level Meters
IEC 61260:1995 Electroacoustics — Octave-band and Fractional—octave—band Filters
ISO/IEC Guideline 98-3 Uncertainty Of Measurement — Part 3: Guide to the Expression of Uncertainty In Measurement (GUM:1995)
3 Terms and Definitions
For the purpose of this document, the following terms and definitions apply.
Foreword i
Introduction iii
1 Scope
2 Normative References
3 Terms and Definitions
4 Reference Meteorological Conditions
5 Test Rooms
6 Instrumentation
7 Definition, Location, Installation and Operation of Noise Source Under Test
8 Measurement Surface
9 Determination of Sound Power Levels and Sound Energy Levels
10 Measurement Uncertainty
11 Information to be Recorded
12 Test Report
Annex A (Normative) General Procedures for Qualification of Anechoic and Hemi-Anechoic Rooms
Annex B (Normative) Qualification Procedure for Spaces Within Test Rooms Used in the Determination of Sound Power Levels and Sound Energy Levels of Specific Noise Sources
Annex C (Normative) Calculation of A-Weighted Sound Power Levels And A-Weighted Sound Energy Levels from One-Third-Octave Band Levels
Annex D (Normative) Array of Microphone Positions on A Spherical Measurement Surface in A Free Field
Annex E (Normative) Arrays of Microphone Positions on A Hemispherical Measurement Surface in A Hemi-Free Field
Annex F (Normative) Coaxial Circular Paths of Microphones on A Hemispherical Measurement Surface in A Hemi-Free Field
Annex G (Normative) Meridional Paths of Microphones on A Hemispherical Measurement Surface in A Hemi-Free Field
Annex H (Normative) Spiral Paths of Microphones on A Hemispherical Measurement Surface in A Hemi-Free Field
Annex I (Informative) Guidance on the Development of Information on Measurement Uncertainty
Annex NA (Informative) Test Room Design Guideline
References
