JB/T 4330-1999 Determination of noise from refrigeration and air conditioning equipment
Some standard content:
JB/T4330--1999
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Preface
This standard is a revision of JB4330-86 "Engineering Method for Determination of Noise and Sound Power Level of Manufacturing and Air-conditioning Equipment"|| tt||The original standard was first released in 1986. There are still deficiencies in the implementation. For example, the test method of two reflective surfaces is difficult to implement. In order to coordinate with relevant standards, the content has been appropriately modified. Modifications were made, and the measurement of sound pressure level was added to the standard appendix. Appendix A, Appendix B, Appendix C and Appendix D of this standard are all appendices of the standard. Appendix E of this standard is a reminder appendix.
This standard replaces JB4330--86 from the date of implementation. This standard is proposed and administered by the National Refrigeration Equipment Standardization Technical Committee. The organization responsible for drafting this standard is: Hefei General Machinery Research Institute. The main drafters of this standard: Meng Zhaopeng, Lin Ze'an. 55
1 Scope
Mechanical Industry Standard of the People's Republic of China
Determination of noise emitted by refrigeranting and air conditioning equipmentsJB/T 4330—- 1999
Replacing JB4330-86
This standard specifies the method for measuring the noise sound power level under free field conditions on the reflection plane. Appendix C (the appendix of the standard) gives the measurement of the noise sound pressure level. Method; Appendix D (standard appendix) gives the measurement method of air conditioner (machine) noise sound pressure level. This standard applies to refrigeration and air-conditioning equipment and components (hereinafter collectively referred to as units) that are assembled and shipped from the factory. 2 Referenced standards
The provisions contained in the following standards constitute provisions recommended for this standard by being quoted in this standard. At the time of publication, the editions indicated were valid. All standards are subject to revision and parties using this standard should explore the possibility of using the latest version of the standards listed below. GB/T3785—1983 Electrical and acoustic properties and test methods of sound level meters JJG176—1984 Verification regulations for sound calibrators JJG188—1984 Verification regulations for sound level meters
3 Test environment
3.1 Reflection plane| |tt||The reflective plane shall be a flat surface constructed of concrete, asphalt, terrazzo or other similar solid material, and shall be larger than the projection of the measuring surface onto it.
3.2 Suitable test environment
The unit should perform noise testing in a half space on a reflective plane. The ideal test environment is one where there are no other reflectors other than the specified reflective plane. Appendix A (subject appendix) gives the identification method of the test environment. 4 Quantities to be measured and measurement errors
4.1 Quantities to be measured
A-weighted sound power level and seven octave sound power levels with center frequencies between 125Hz and 8000Hz. 4.2 MeasurementbzxZ.net
The standard deviation of the A-weighted sound power level is approximately 2dB. The standard deviation of the octave sound power level is shown in Table 1. Approved by the Ministry of Machinery Industry on 1999-07-12 56
2000-01-01 Implementation
Octave center frequency
Hz
125
250 -~500
1 000 ~~ 4 000
8000
JB/T 4330--1999
Table 1
Standard deviation||tt| |dB
3.0
2. 0
1. 5
2.5
Note: The above measurement error refers to the error caused by various factors. Cumulative standard deviation, but does not include changes in sound power caused by changes in unit installation and operating conditions in each measurement. || tt | An extension rod or cable should be used between the sound level meter or other test instrument and the microphone. Octave band analyzers should comply with relevant standards. 5.2 Calibration
Before and after each measurement, a sound level calibrator with an accuracy better than ±0.5dB should be used to calibrate the entire test instrument system at one or more frequencies. The sound level calibrator should be regularly calibrated according to JJG176 Test. Sound level meters and other testing instruments should be regularly calibrated according to JJG188. 6 Installation and operation of the unit
6.1 Installation of the unit
The fixed unit should be installed according to the requirements of the relevant technical conditions, and the mobile unit should be placed directly on the reflective ground; all components should be installed whole. However, additional vibration isolation, sound insulation and sound absorption components should not be added. 6.2 Operation of the unit
The unit should operate continuously under stable working conditions. The following provisions are made for different units: a) Refrigeration compressors and compression condensing units should operate under nominal refrigeration conditions specified in relevant standards. b) For room fan coil air conditioners, air-cooled condensers, etc., they can be tested only with the fan running. Center) Other operating conditions of the unit shall be in accordance with the provisions of the relevant unit test methods. 7 Reference body and measurement surface
7.1 Reference body
The reference body is a minimum rectangular hexahedron that just envelops the unit under test and terminates on the reflection plane. When determining the reference body, small protruding parts on the unit (such as connecting pipes, handles, etc.) will not be considered. 7.2 Measuring surface
The measuring surface is divided into a hemispheric measuring surface and a rectangular hexahedral measuring surface [see Figures B1 and B2 in Appendix B (Standard Appendix)]. 7.2.1 Hemispheric measuring surface
a) For fully enclosed, semi-hermetic refrigeration compressors and other units with smaller sizes, use a hemispheric measuring surface. b) The center of the hemispheric measuring surface is the projection of the geometric center of the base body on the reflection plane. The radius r of the hemispheric measuring surface should not be less than twice the characteristic distance d, the characteristic distance d. Calculate according to formula (1): d. [(0.51,)2+(0.5)→1/2
where d. Characteristic distance, m
LL2L3
-the length, width and height m of the base body.
(1)
The radius r of the hemispherical surface is preferably 1m or 2m. If d. If it is larger than 1m, the rectangular hexahedron mentioned in 7.2.2 should be used to measure the 57
surface.
c) The hemisphere measurement surface area is calculated according to formula (2). In the formula: S - hemisphere measurement surface area, m2 hemisphere measurement surface radius, m.
7.2.2 Rectangular hexahedron measurement surface
JB/T 4330--- 1999
S, = 2 elements r2
(2)
rectangular The hexahedral measurement surface is a rectangular box surface located on a reflection plane that is geometrically similar to the reference body. The measuring surface and the corresponding surface of the base body should be parallel and separated by d. The measurement distance d is specified in Appendix A. The preferred measuring distance is 1 m. The measured surface area is calculated according to formula (3):
S2 = 4(ab + αc + bc)
where: S2
ab-
C||tt ||Measure the surface area, m;
Measure half of the length and width of the surface, m;
Measure the height of the surface, m.
8 The quantity of sound pressure level
8.1 Background noise
8.1.1 In the following cases, the background noise only needs to be measured at one measuring point: a) Background The noise sound pressure level is more than 1QdB lower than the unit noise sound pressure level; b) The background noise source is far away from the test site:
c) The maximum size of the base body is less than 1m.
Otherwise, the background noise should be measured at each measuring point (3)
8.1.2 The background noise is corrected according to Table 2. This standard requires that the measured unit noise sound pressure level and the background The difference in noise sound pressure levels should not be less than 6 dB.
Table 2
The difference between the measured unit noise sound pressure level and the background noise sound pressure level 68
9,10
>10
8.2 Wind speed
Correction amount subtracted from the measured sound pressure level 1.0
0.5
o
The wind speed near the measuring point during the test should be less than 6m/s ( Equivalent to Category 4 wind). A wind hood should be used when the wind speed is greater than 1m/s. 8.3 Measuring point locations
dB
8.3.1 All measuring point locations should be on the measuring surface determined in 7.2. Figures B1 and B2 in Appendix B show the measuring points on the measuring surface. Location, Table B1 and Table B2 give the coordinates of each measuring point. 8.3.2 A total of 10 measuring points are arranged on the hemispheric measuring surface (see Figure B1 and Table B1). 8.3.3. The measuring points on the rectangular hexahedral measuring surface are divided into basic measuring points and additional measuring points. There are 9 basic measuring points and 8 additional measuring points (see Figure B2 and Table B2).
8.3.4 Additional measuring points are required under the following circumstances: a) any side of the reference body is greater than 2d (d is the measurement distance); b) the maximum and minimum sound pressure levels measured on the basic measuring points The difference exceeds the number of measuring points; c) When the unit under test is very large or a smaller measuring distance is selected, additional measuring points should continue to be added so that the distance between measuring points on the measuring surface does not exceed 2d. and is evenly distributed.
8.3.5 Reduction in the number of measuring points
58
JB/T 4330—1999
For a certain type of unit, if the test shows that the number of measuring points is reduced, If the difference between the sound power level and the sound power level measured at the basic measuring points is within ±1dB, the number of measuring points can be appropriately reduced. 8.4 The microphone used to measure
should be facing the direction of the unit under test. The sound level meter should use slow time weighting characteristics for measurement. When the sound level meter pointer swings not more than ±3dB, take the average of the maximum and minimum sound pressure levels during observation. A weighting and the octave with a center frequency greater than 160Hz , the observation time is at least 10s; if the center frequency is less than 160Hz octave, the observation time is at least 30$. When the sound level meter pointer swings greater than ±3dB, then: a) Analog instruments or digital instruments with longer time constants should be used. Measurement with an integral sound level meter: b) Use the "slow" time weighting characteristic of the sound level meter to measure the periodically changing unsteady noise, record the sound pressure level and duration within a cycle, and calculate the sound pressure level and duration of a cycle. Energy average. 8.5 Correction of the measurement environment
When there are unnecessary reflectors in the measurement environment, the measurement results should be corrected. See Appendix A for the method of determining the environmental correction value K. |9 Calculation of the average sound pressure level and sound power level on the measured surface 9.1 Calculation of the average sound pressure level on the surface
Measure the average sound pressure level I on the surface, calculated according to formula (4): L, = 10lg(1/N )(
(100.11)
where: L,---Measurement surface average A-weighted or octave sound pressure level, dB (base value is 20μPa); Ipi-according to 8.1 The i-th point A-weighted or octave sound pressure level after correction of background noise, dB (reference value is 20uPa); N——the total number of measuring points
9.2 Calculation of sound power level||tt| |Sound power level is calculated according to formula (5):
Lw = (L,- K)+ 1olg(S/S.)
where: Lw——A-weighted or octave Sound power level, dB (base value is 1 pW), I, - average sound pressure level on the measurement surface, dB (base value is 20 μPa); K
Environment correction value, dB (see Appendix A)| |tt||-Measurement surface area, m;
S
So
The reference area is 1m.
10 Test records
The test records should include The following content, the recommended record form format is shown in Appendix E (Appendix of Prompt). 10.1 Unit under test
a) The model, name, manufacturer and factory number of the unit and other relevant parameters; b) The testing process of the unit. Condition parameters.
10.2 Acoustic environment
(4)
(5)
Reflection plane conditions, test chamber volume, total surface area and sound absorption treatment conditions should be recorded. And draw a schematic diagram of the sound source location. For outdoor measurements, the wind speed, distance from the measuring point to the nearest reflector, etc. should be recorded. 10.3 Test instrument
a) The model, name, manufacturer and factory number of the instrument; b) Date and department of instrument inspection.
10.4 Acoustic data
59
1999
JB/T 4330-
a) Reference body size, measurement surface The size and surface area of ??the b) measuring point location, and draw a schematic diagram of the measuring point location; c) A-weighted or octave sound pressure level at each measuring point; d) background noise sound pressure level and corresponding correction value, according to Appendix A Determined environmental correction value K; e) Measured surface average A-weighted or octave sound pressure level and calculated sound power level. 10.5 Meteorological conditions
Temperature, relative humidity and atmospheric pressure.
10.6 Testers, time, location and other circumstances that need to be explained. 11 Test report
The test report includes the following contents. See Appendix E for the recommended test report form. a) Unit model, name, manufacturer and broadcast number; b) Test conditions:
c) A-weighted sound power level and octave sound power level d) The report should indicate that it is based on this standard measured. 60
A1 Overview
JB/T4330-1999
Appendix A
(standard appendix)
Qualification method of test environment
This appendix specifies the use of the absolute comparison method and the reverberation time method to determine the environmental correction value K. A1.1 No environmental correction (i.e. K=0) is required under the following circumstances: a) an outdoor venue with no reflectors within 10m of any measuring point; b) a semi-anechoic room certified according to relevant standards. Note: Sound reflectors mainly refer to buildings and some larger equipment. When the width of an obstacle close to the sound source (such as the diameter of piles and columns) is greater than one-tenth of its distance from the sound source, it is considered to be a sound reflection. reflector. A1.2 Environmental correction value K | Environmental modifier. However, the measurement distance should not be less than 0.5 m;
c) When the K value is greater than 2dB and less than 7dB, measure the A-weighted sound power level according to the test procedures given in this standard. If it is used for similar units in the same test When comparing sound power levels in the environment, the standard deviation shall not be greater than 3dB. A2 absolute comparison method
A2.1 method
The absolute comparison method is also called the standard sound source method. The standard sound source should have the acoustic characteristics stipulated in the relevant standards and be regularly verified in accordance with the relevant regulations. The qualified standard sound source is placed in the same test environment of the unit under test, and the sound power level of the standard sound source is measured using the same measuring surface and measuring point as the unit under test (no environmental correction item is required, K-0) . When the standard sound source is placed in multiple locations (see A2.2), measure the average sound pressure level L on the surface and calculate it according to formula (A1): where: L.
N
M-
Lpi
L,= 10lglNM
100.1 p
il jt
Measurement surface average Sound pressure level, dB (reference value is 20μPa); total number of measuring points:
Number of standard sound source placement points:
The sound pressure level of the i-th measuring point and the i-th placement point, dB (reference value is 20μPa). The sound power level is calculated according to formula (5) (let K0 in the formula), then the K value is obtained from formula (A2): K= Lw-Lwo
Where: K environment correction value, dB||tt| |Lw
The sound power level of the standard sound source measured on site (no environmental correction is required), dB (the reference value is 1pW); Lwo
The sound power level of the standard sound source calibration, dB . A2.2 Placement of standard sound sources
According to different situations, the placement of standard sound sources is divided into three types: substitution method, top placement method and side placement method. a) Substitution method
(Al)
(A2)
When the unit under test can be moved away from the test site, the substitution method is used. The standard sound source placement point is the projection of the geometric center of the reference body on the reflection surface,
b) Top method and side method
61
JB/T4330—1999||tt ||For the unit installed on site, when it cannot be moved from the test site, the top or side method can be used for on-site testing. The overhead method is to place the standard sound source on the top of the unit under test; the side method is to place the standard sound source in the middle of each side of the unit. When using the top-mounted method or the side-mounted method, the surface of the unit should be completely sound reflective. When other objects need to be used to support the standard sound source, the surface of the support should not be larger than the size of the bottom of the standard sound source.
A3 reverberation time method
This method is suitable for indoor environments with a shape that is approximately cubic (the ratio of the largest to the smallest dimensions is less than 3). The environmental correction value is calculated according to formula (A3): || tt||4
K = 10lg(1 +
A/S
where: K-
S
environmental correction value, dB;
Measure the surface area, m,
A—the total sound absorption of the room, m\.
The total sound absorption of the room is obtained by measuring the reverberation time, according to the formula (A4 ) Calculation: A = 0.16(V/T)
—the volume of the room, m2,
where, V-
T octave reverberation time, S.
......(A3)
(A4)
Please refer to relevant standards for the measurement of reverberation time. When this method is adopted, the A-weighted sound power level is determined by Force synthesis in Chapter A4. The method of synthesizing A-weighted power level from A4 octave sound power level. The A-weighted sound power level from A4 octave sound power level is calculated according to formula (A5): LwA = 10lg 2
C100.1(w. +c,)
where: LwA--A-weighted sound power level, dB (base value is 1pW); Lwi-
sound power level of the ith octave, dB (baseline value is 1pW); the i-th octave A-weighted attenuation (see Table A1). C,
Table A1 octave center frequency A-weighted attenuation number:
1
2
3
5||tt| |6
7
62
Borrowing band center frequency
Hz
125
250
500|| tt||1000
2000
4000
8000
C,
dB
16.1
-8. 6
-3.2
0
+1.2
+1.0
1.1
(A5)
JB/T4330— 1999
Appendix B
(standard appendix)
Reference body, measuring surface and measuring point weight
The measuring point position on the B1 hemispheric measuring surface is shown in Figure B1 and Table B1. 2
Reference body
Measurement surface
Measuring point number
I
2
3
4
5
6
7
88
9
10
X/r
— 0.99
0.50
0.50
0.45
—0.45
0.89
0.33
--0.66||tt| |0.33
0
010
Figure B1
Table B1
Y/r
0
0.86|| tt||0.86
0. 77
0.77
0
0.57
0
-0.57
0| |tt||B2 rectangular hexahedral measuring surface and measuring points are shown in Figure B2 and Table B2. 3
o
Z/r
0.15
0.15||tt| |0.15
0.45
0.45
0.45
0.75
0.75
0.75
1.0
63
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