GB/T 6882-2016 English PDF (GBT6882-2016)

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GB/T 6882-2016: 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
GB/T 6882-2016
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 17.040
A 59
GB/T 6882-2016 / ISO 3745:2012
Replacing GB/T 6882-2008
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
(ISO 3745:2012, IDT)
ISSUED ON: FEBRUARY 24, 2016
IMPLEMENTED ON: SEPTEMBER 01, 2016
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 4 
Introduction ... 6 
1 Scope ... 7 
2 Normative references ... 8 
3 Terms and definitions ... 8 
4 Reference meteorological conditions ... 16 
6 Instrumentation ... 20 
7 Definition, location, installation and operation of noise source under test ... 21 
8 Measurement surface ... 24 
9 Determination of sound power levels and sound energy levels ... 26 
10 Measurement uncertainty ... 39 
11 Information to be recorded ... 44 
12 Test report ... 46 
Annex A (normative) General procedures for qualification of anechoic and hemi-
anechoic room ... 47 
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 ... 57 
Annex C (normative) Calculation of A-weighted sound power levels and A-
weighted sound energy levels from one-third-octave band levels ... 60 
Annex D (normative) Array of microphone positions on a spherical
measurement surface in a free field ... 62 
Annex E (normative) Arrays of microphone positions on a hemispherical
measurement surface in a hemi-free field ... 64 
Annex F (normative) Coaxial circular paths of microphones on a hemispherical
measurement surface in a hemi-free field ... 69 
Annex G (normative) Meridional paths of microphones on a hemispherical
measurement surface in a hemi-free field ... 70 
Annex H (normative) M Spiral paths of microphones on a hemispherical
measurement surface in a hemi-free field ... 73 
Annex I (informative) Guidance on the development of information on
measurement uncertainty ... 74 
Annex NA (informative) Test room design guidelines ... 88 
Bibliography ... 90 
Foreword
This Standard is one of the series of standards of determination of sound power
levels and sound energy levels of noise sources using sound pressure.
This Standard was drafted in accordance with the rules given in GB/T 1.1-2009.
This Standard replaces GB/T 6882-2008 "Acoustics - Determination of sound
power levels of noise sources using pressure - Precision methods for anechoic
and hemi-anechoic rooms".
Compared with GB/T 6882-2008, the main modifications in this Standard are
as follows:
- added the content of terms and definitions;
- the content of measurement uncertainty has been greatly revised; added
the content of cyclic comparison test and mathematical model method to
determine the standard deviation of reproducibility;
- improved the "background noise requirement" to the "background noise
criterion"; respectively formulated the relative value criterion and the
absolute value criterion; supplemented the remarks of 5.2.2 absolute
value criterion, so as to make the remarks more detailed and clearer;
- modified the definition and expression of directivity index;
- added the baseline weather conditions;
- increased microphone array positions from 20 to 40;
- kept the Annex K (informative) "Guidelines for design of test room" in GB/T
6882-2008 as Annex NA of this Standard; this annex was deleted from
ISO 3745:2003 when ISO 3745:2012 was revised; taking into account the
needs of China's acoustic measurement and precision testing room
construction, this Standard retains this annex.
This Standard uses translation method to identically adopt ISO 3745:2012
"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" (English version).
The Chinese documents which have consistency with the international
normative reference in this Standard are as follows:
- GB/T 3241-2010, "Electroacoustics - Octave-band and fractional-octave-
band filters" (IEC 61260:1995+AM1:2001, MOD)
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 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 (or, in the
case of impulsive or transient noise emission, the sound energy level) produced
by the 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 includes the one-third-octave bands
with mid-band frequencies from 100 Hz to 10 000 Hz. In practice, the range is
extended or restricted to frequencies beyond or within these limits, to those
between which the test room is qualified for the purposes of the measurements.
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 bursts 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 limited bands of frequency and with frequency weighting A applied. The
uncertainty conforms to GB/T 19052-2003, accuracy grade 1 (precision grade).
2 Normative references
The following referenced documents are indispensable for the application of
this document. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (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
ISO 9613-1:1993, Acoustics - Attenuation of sound during propagation
outdoors - Part 1: Calculation of the absorption of sound by the atmosphere
IEC 61183:1994, Electr...