Some standard content:
JB/T8098--1999
This standard is a revision of JB/T8098--95 "Measurement and Evaluation Method of Pump Noise". Compared with JB/T8098-95, the main technical content of this standard has been changed as follows:
1. Some new content has been added, among which "Sound Pressure Level Measurement" has made detailed provisions on the selection of measurement surface, the location of basic microphone and additional microphone, the influence of environmental conditions, and the measurement method. 2. The calculation accuracy of A-weighted surface sound pressure level and A-weighted surface sound power level has been improved. The measurement environment has changed from only allowing one reverse surface to the sound source close to two reflecting surfaces, and the corresponding measurement point layout principles and schematic diagrams are given for each situation. 3. Four appendices have been added.
This standard replaces JB/T8098-95 from the date of implementation. Appendix A, Appendix B, and Appendix C of this standard are all standard appendices. Appendix D of this standard is a prompt appendix. This standard is proposed and managed by the National Pump Standardization Technical Committee. This standard was drafted by: Shenyang Pump Research Institute. The main drafters of this standard are: Wang Shimin, Gong Chuanjia. 688
JB/T 8098—1999
This standard is a simple method for determining the sound power level of pump noise formulated in accordance with GB/T3768--1996. In addition to the simple method, the national standard also has the engineering method and the precision method. This series of standards specifies different methods for determining the sound power level of pumps or their combinations. When selecting these standards, the best choice should be made according to the general guidelines given in GB/T14367 based on the purpose and conditions of noise measurement. The above standards only give general principles for the installation and working conditions of pumps. For a specific type of pump, the technical requirements for its installation and working conditions need to refer to the corresponding noise test specifications.
This standard specifies a method for measuring the sound pressure level on the measurement surface of the envelope sound source to calculate the sound power level. The envelope surface method is applicable to all three accuracy levels (see Table 0.1), and the accuracy level of this standard is level 3. When using this standard, it is required to meet some of the identification criteria listed in Table 0.1. If the corresponding standards cannot be met, the methods of ISO3747 or ISO 9614 can be tried.
Specific to a certain type of pump equipment, its noise test specifications should be based on the series of standards for the determination of sound power levels of noise sources, and there should be no contradictions.
When measuring between typical pumps where the sound source is placed, corrections for background noise or unwanted sound reflections are required. The method specified in this standard allows the A-weighted sound power level to be determined directly from the measured A-weighted sound pressure level. This standard calculates the sound power level from the measured sound pressure level based on the premise that the sound power output of the sound source is proportional to the mean square sound pressure averaged over time and space.
Table 0.1 List of national standards for different accuracy levels for measuring the sound power level of noise sources on reflecting surfaces using the envelope surface method Parameters
Test environment
Test environment suitability assessment criteria!
Sound source volume
Noise characteristics
Limitation on background noise!\
Number of measuring points
Instrument:
Sound level meter shall at least meet
Integrating sound level meter shall at least meet
Band-pass filter shall at least meet
GB/T6882 precision method
Semi-anechoic room
K2≤0.5dB
It is best to be less than 0.5% of the test
room volume||t t||GB/T3767 Engineering method
Outdoor or indoor
Unrestricted
Limited only by effective test environment
GB/T3768 Simple method
Outdoor or indoor
K≤7dB
Unrestricted
Limited only by effective test environment
All kinds of noise (broadband, narrowband, discrete frequency, steady state, non-steady state, pulse) AL≥10dB
(If possible,>15dB)
Ki≤0.4dB
a) Type 1 specified in GB/T3785
b) Type 1 specified in IEC804
c) Provisions of relevant standards
AL≥6 dB
(if possible,>15dB)
Ki≤1.3 dB
8) Type 1 specified in GB/T3785
b) Type 1 specified in IEC804
c) Provisions of relevant standards
L≥3dB
a) Type 2 specified in GB/T3785
b) Type 2 specified in IEC804
JB/T 8098—1999
The accuracy of the LWA determination method is expressed by
the standard deviation of the reproducibility
Table 0.1 (end)
GB/T6882 Precision method
a≤1dB
GB/T3767 Engineering method
GB/T3768 Simple method
Kz<5 dB,
5 dB≤K,≤7dB,
When the commercial scattered pure tone accounts for the main component,
increase dB
1) When measuring the sound power spectrum, K, and K, should meet the requirements in each frequency band within the test frequency range; when measuring the A-weighted sound power level, K1A and K2A also use the above values.
2) Under given conditions, it is allowed to reduce the number of measuring points. 690
1 Scope
1.1 General
Methods of measuring and evaluating noise of pumpsJB/T 8098—1999
Replaces JB/T8098—95
This standard specifies the method and evaluation method for measuring the sound pressure level on the measuring surface of the envelope pump to calculate the sound power level of the noise source. At the same time, the requirements for the test environment, measuring instruments, and the calculation methods of the surface sound pressure level and sound power level are given. This standard is applicable to various types of pumps and speed-adjusting hydraulic couplings for pumps, except for submersible pumps and reciprocating pumps. The noise test specification should give detailed instructions on the installation, load, working conditions, measurement surface and microphone array selection of the sound source to be measured.
Note 1: For a specific type of pump, its noise test specification should give detailed information on the selected special measurement surface, because the use of measurement surfaces of different shapes will result in different evaluations of the sound power level of the sound source. 1.2 Types of noise and noise sources
The methods specified in this standard are applicable to the measurement of various types of noise. Note 2: The classification of noise (steady state, unsteady state, quasi-steady state, pulse, etc.) should comply with the relevant provisions of GB/T14259. This standard is applicable to sound sources of various types and sizes of pumps. 1.3 Test environment
This standard is applicable to indoor or outdoor test environments that meet the requirements and have one or more reflective surfaces. 1.4 Measurement uncertainty
For a sound source that radiates steady-state narrowband noise, the reproducibility standard deviation of the A-weighted sound power level measured in accordance with this standard is, except for individual cases, equal to or less than 3dB (K2A<5dB) or 4dB (5dB≤K2A≤7dB). For a sound source that radiates discrete pure tones, the reproducibility standard deviation is generally increased by 1dB (see Table 1). There is a high probability that there is a difference within the uncertainty range between the single value of the sound power of a noise source measured in accordance with this standard and its true value. The uncertainty in the measurement of the sound power level comes from the combined influence of the environmental conditions and experimental techniques of the measurement laboratory. If a specific noise source is measured for its sound power level in accordance with this standard at different test sites, the measurement results will show discreteness. The calculation of the standard deviation of the measurement results is shown in GB/T14573.4. Except for individual cases, the above standard deviation shall not exceed the value in Table 1. The reproducibility standard deviation GR given in Table 1 takes into account the cumulative effect of uncertainty in the measurement process, but does not include changes in sound power output caused by changes in working conditions (speed, power supply, voltage) or installation conditions. The measurement uncertainty is not only related to the reproducibility standard deviation, but also to the required confidence level. For example, for a normally distributed sound power level, when the confidence level is 90%, the true value of the sound power level of the sound source is within ±1.645g of the measured value. When the confidence level is 95%, the true value is within ±1.960e of the measured value. See GB/T14573 series for details. 1.5 Impact of noise
This standard can be used to understand the noise level of pumps or units in a more standardized way. When it is necessary to measure the sound power level of the pump sound source, the influence of the noise of the prime mover (electric motor, internal combustion engine, etc.) should be considered. If necessary, measures such as sound insulation (such as soundproof cover) should be taken to reduce the impact of the prime mover. Approved by the State Bureau of Machinery Industry on August 6, 1999 and implemented on January 1, 2000
JB/T8098—1999
Table 1A The maximum value of the reproducibility standard deviation of the weighted sound power level applies to
Sound sources with relatively "flat" noise spectra within the test frequency range Sound sources with discrete pure tones as the main components
1 If K2A ≥ 5 dB, R may be 1 dB larger than the value in the table. The maximum value of the reproducibility standard deviation R
2 The noise test specification for a specific type of noise source may give a lower reproducibility standard deviation. 3
The standard deviations listed in the table are the combined effects of the measurement conditions and methods specified in this standard, and do not include the influence of the sound source itself. They are caused by the following aspects: variations between measurement sites, including outdoor environmental and climatic conditions, indoor test room geometry, absorption of test room boundaries, acoustic characteristics of reflecting surfaces, background noise; instrument calibration forms; and variations in test techniques, including the shape and size of the measurement surface, the number of measurement points and microphone positioning, sound source position, integration time, and determination of environmental corrections (if any). The standard deviation is also affected by the error introduced by near-field measurements, which is related to the characteristics of the sound source and generally increases when the measurement distance is small and the frequency is low (below 250 Hz). If a given sound source is measured at several test sites using similar instruments, the consistency of the measured sound power level results may be better than the consistency reflected by the standard deviation in the table. For a specific type of sound source with similar size, similar sound power spectrum and similar working conditions, the reproducibility standard deviation may be smaller than the value in the table. When formulating noise test specifications with reference to this standard, if it is proved feasible through appropriate laboratory verification, a smaller standard deviation than the value in the table can be marked in the noise test specification. 6 The reproducibility standard deviation in the table includes the uncertainty of repeated measurements of the same noise under the same conditions (standard deviation of repeatability). This uncertainty is generally much smaller than the uncertainty caused by the exchange of laboratories. For special sound sources, if it is difficult to maintain stable working conditions and installation conditions, the standard deviation of repeatability may not be smaller than the value given in the table. In this case, it is difficult to obtain a reproducible sound power level, which should be recorded and explained in the test report.
7 The method of this standard and the standard deviation given in the table are applicable to the measurement of a single machine. The characteristic representation of the sound power level of a batch of machines of the same type involves a random sampling technique with a specified confidence interval, and the result is expressed as a statistical upper limit. When applying these techniques, the total uncertainty must be known or estimated, including the product standard deviation defined in GB/T 14573.2, which is the deviation in sound power output between individual machines in a batch of machines. Statistical methods for machine batch characteristics are given in GB/T 14573.4. 2 Cited standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard was published, the versions shown were valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB3102.7—-1993 Acoustic quantities and units GB/T 3767-1996
Acoustics Determination of sound power level of noise source by sound pressure method Engineering method for approximate free field above reflecting surface GB/T3768-—1996 Acoustics Determination of sound power level of noise source by sound pressure method Simple method using envelope measuring surface above reflecting surface GB/T3785—1983
Electrical and acoustic properties and test methods of sound level meter GB/T3947~1996 Acoustics Terminology
GB/T4129-1995 Acoustics
Determination of sound power level of noise source Performance requirements and calibration of standard sound source GB/T6882—1986 Acoustics Determination of sound power level of noise source Precision method in anechoic chamber and semi-anechoic chamber GB/T14259-1993 Acoustics Guide to calibration of measurement of airborne noise and assessment of its impact on people GB/T14573.1-- 1993 Acoustics Statistical methods for determining and verifying the specified noise radiation values of machinery and equipment Part 1: Overview and definitions
GB/T14573.2-1993 Acoustics Statistical methods for determining and verifying the specified noise radiation values of machinery and equipment Part 2: Determination and verification methods for the label value of a single machine GB/T14573.4-1993 Acoustics Statistical methods for determining and verifying the specified noise radiation values of machinery and equipment Part 4: 692
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Determination and verification methods for the label value of a batch of machines GB/T16538--1996 Acoustics Sound pressure method Determination of sound power level of noise source Simple method using standard sound source IEC804--1985 Integrating average sound level meter
3 Definitions
This standard adopts the following definitions. Other acoustic terms, quantities and units shall be in accordance with the provisions of GB/T3947 and GB3102.7. 3.1 Time-averaged sound pressure level Lpeaq,Ttime-averaged sound pressure level Lpeq.T is the sound pressure level of a continuous steady-state sound. In the measurement time interval T, it has the same mean square sound pressure as the measured sound that varies with time. It is also called the equivalent continuous sound pressure level.
The time-averaged sound pressure level LPey.T is calculated according to formula (1): Lpea. r(dB) =1olg
=10lg
Note 3: The time-averaged sound pressure level is generally weighted and represented by LA, r. 100.1,dt
Tp?(t)dt
3. 2 Single-event sound pressure level Lp.ls single-event sound pressure level Lp.bs（1）
The time-integrated sound pressure level of an independent single-event over a specified time interval T (or a specified measurement time T), T. The sound pressure level Lp.la normalized to a single event of 1s is calculated according to formula (2): Lp2(t)dt
Lp.b(dB) =10lg[]. P
=Lpa, + 10lg[.
3. 3 Surface sound pressure level Lp surface sound pressure level Lp (2)
The energy average of the time-averaged sound pressure level at all microphone positions on the measurement surface plus the background noise correction K, and the environmental correction K2, dB.
3.4 Measurement surface measurement surface An imaginary geometric surface that envelops the sound source and has an area of S, on which the measurement points are located. The measurement surface terminates on one or more reflecting surfaces. 3.5 Frequency range of interest Generally speaking, the frequency range of interest includes an octave band with a center frequency of 125 to 8000 Hz. 3.6 reference box
imaginary surface of the smallest rectangular parallelepiped that just envelops the sound source and ends on one or more reflecting surfaces. 3.7 characteristic source dimension d. characteristle source dimension ds half the length of the diagonal of the box formed by the reference box and its virtual image in the adjacent reflecting surface. 3.8 measurement distance d measurement distance d the vertical distance between the reference box and the box-shaped measurement surface. 3.9 measurement radius r measurement radius r the radius of the hemispherical measurement surface.
3.10 background noise background noise from all other sound sources other than the sound source program under test. Note 4: Background noise includes airborne sound, structure-borne vibration, instrument electrical noise, etc. 3.11 background noise correction K, background noise correction term introduced by the effect of background noise on the surface sound pressure level, dB. K, is frequency-dependent and is represented by K1A in the case of A-weighting.
3.12 Environmental correction K, environmental correction K, 693
JB/T 8098—1999
A correction term introduced by the effect of sound reflection or sound absorption on the surface sound pressure level, dB. K, is related to the frequency and is expressed as K2A in the case of A weighting.
3.13 Impulsive noise index (impulsiveness) A quantity used to characterize the "impulsiveness" of the noise radiated by the sound source, dB. 4 Acoustic environment
4.1 General
The test environment applicable to this standard includes a room or outdoor flat space that meets the requirements of 4.2, and the background noise should meet the requirements of 4.3. 4.2 Criteria for judging the suitability of the test environment
Appendix A (Appendix to the standard) gives the method for determining the environmental correction K2A. This standard requires that the environmental correction K2A is less than or equal to 7dB. Note 5: If the environmental correction K2A is greater than 7dB, it is recommended to use the relevant methods in GB/T16538. 4.3 Background noise standard
The A-weighted sound pressure level of the background noise averaged at the microphone position should be at least 3dB lower than the sound pressure level being measured. 5 Measuring instruments
5.1 General
The instrument system including microphones and cables shall meet the requirements of Type 2 in GB/T3785-1983. When using an integrating sound level meter, it shall meet the requirements of Type 2 in IEC.804:1985. The filters used shall meet the requirements of relevant national standards and industry standards. 5.2 Calibration
Before and after each measurement, the entire measurement system shall be calibrated at one or more frequency points within the test frequency range using a sound calibrator with an accuracy better than ±0.3dB. The sound calibrator and measurement system shall be qualified by metrological verification every year. 5.3 Microphone wind oxygen
When measuring outdoors, it is recommended to use a wind shield to ensure that the measurement accuracy of the instrument is not affected by wind. 6 Pump installation and working conditions
6.1 Installation
When installing pumps and test equipment, the following points should be noted: a) When measuring in the laboratory, the outlet throttle valve should be installed far away from the pump; b) When the suction and discharge pipe noise is too loud, measures should be taken to reduce the noise impact; c) The noise impact from other test equipment should be minimized. 6.2 Working conditions
When measuring the noise of vane pumps such as centrifugal pumps, mixed flow pumps, axial flow pumps, etc., it should be carried out at the specified speed (allowable deviation ±5%) and specified flow rate. When measuring the noise of positive displacement pumps such as gear pumps, vane pumps, screw pumps (except reciprocating pumps), it should be carried out at the specified speed (allowable deviation ±5%) and specified working pressure.
7 Measurement of sound pressure level
7.1 Selection of measurement surface
In order to facilitate the positioning of the microphone on the measurement surface, a reference body should be set. When setting the reference body, units that protrude from the sound source but do not radiate significant sound energy may not be considered. For different types of equipment, the protruding units should be noted in the specific noise test specifications. The position of the sound source to be measured, the measurement surface and the microphone position are set by a coordinate system. The X-axis and Y-axis of the coordinate system are located on the ground and are parallel to the length and width of the reference body, with a specific sound source size d. As shown in Figure 1. 694
do = V/2)2+ +
JB/T8098—1999
do=(1/2)2 +(12/2) +
a) Reference body on one reflection plane
b) Reference body on two reflection planes
d,=+n+
c) Reference body on three reflection planes
Figure 1 Reference body and characteristic sound source size d. Example of relationship with the origin Q of the coordinate system The following two shapes can be used for the measurement surface: a) a hemispherical or partially hemispherical surface with radius r, b) a rectangular parallelepiped surface with all sides parallel to the corresponding base body. For sound sources located in rooms or spaces with unfavorable acoustic conditions (e.g. many reflectors, high background noise), a smaller measurement distance can be selected. Generally, a parallelepiped measurement surface is specified. Sound sources are often installed or tested in large outdoor spaces with satisfactory acoustic conditions, and a larger measurement distance is generally selected. Hemispherical measurement surfaces are preferred. Directivity measurements require a hemispherical or partially hemispherical measurement surface. Measurements of a series of similar sound sources (e.g. machines of the same model or the same type) require the use of measurement surfaces of the same shape. Note 6: For detailed information, refer to the special noise test specifications for the sound source being studied. The composition of the reference body, the shape and size of the measurement surface, and the measurement distance d or hemispherical radius are described in the test report.
7.2 Hemispherical measurement surface
The center of the hemisphere is located at the center of the box formed by the reference body and its virtual image in the adjacent reflecting surface (origin Q in Figure 1). The radius r of the hemispherical measurement surface should be greater than or equal to twice the size d of the characteristic sound source and not less than 1m. The hemispherical radius should adopt one of the following values (m): 1, 2, 4. When the radius is too large, the environmental conditions in Appendix A are difficult to meet, and these radii should not be used.
7.2.1 Area of hemispherical measurement surface and basic microphone position 695
JB/T 8098-1999
When there is only one reflecting surface, the area of the imaginary hemispherical surface where the microphone position is located is S=2 yuan. When the sound source to be measured is located in front of a wall, S=r2. If it is located in a corner, S=0.5 yuan r2. The microphone positions on the hemispherical surface are shown in Figures B1 and B2 in Appendix B (Standard Appendix). Figure B1 shows four basic microphone positions, which are connected with equal areas on the surface of a hemisphere with radius r. If the sound source is placed close to more than one reflecting surface, refer to Figure B3 in Appendix B to set the appropriate measurement surface and microphone positions.
7.2.2 Additional microphone positions on the hemispherical measurement surface Additional microphone positions are required on the measurement surface in the following cases: a) the range of sound pressure level values measured at the basic microphone positions (i.e. the difference between the highest and lowest sound pressure levels, dB) exceeds twice the number of basic measurement points;
b) the noise radiated by the sound source is highly directional; c) a loud sound source, whose noise is radiated outward only through a small local area of the sound source, such as an opening in a closed machine.
For the hemispherical surface microphone array, the additional four measurement points are determined by rotating the original array of Figure B1 by 180° around the Z axis (see Table B1 and Figure B2). Note that the points on the Z axis of the new array coincide with the vertices of the original array, so that the total number of microphone positions increases from 4 to 7. For conditions b) or c), use additional microphone positions in the high noise radiation area of the measurement surface (see 7.4.1). 7.3 Parallelepiped measurement surface
The measurement distance d is preferably 1m, at least 0.15m. d should be selected from the following values--(m): 0.15, 0.25, 0.5, 1, 2, 4, 8. The measurement distance of the sound source should be greater than 1m. When selecting d, the environmental requirements given in Appendix A should be met first. 7.3.1 Area and microphone positions of parallelepiped measurement surface The measurement surface where the microphone position is located is an imaginary surface with an area S, an enveloping sound source, each side parallel to the side of the reference body, and a distance d (measurement distance) from the reference body. The microphone positions on the parallelepiped measurement surface are shown in Figures C1 to C8 in Appendix C (Standard Appendix). According to Figures C1 to C6, the area S of the measurement surface is given by formula (3): S = 4(ab + ac + bc)
a = 0.5l + d
b = 0.5l2 + d
c = h + d
where l1, l2, l3 are the length, width and height of the base body respectively. (3)
If the sound source is placed close to more than one reflecting surface, an appropriate measurement surface should be set with reference to Figures C7 and C8 in Appendix C. The calculation of the measurement surface area S in this case is given in the respective figures. The microphone positions are arranged according to Figures C1 to C6. 7.3.2 Additional microphone positions on the parallelepiped measurement surface Additional microphone positions are required on the parallelepiped measurement surface in the following cases: a) The range of sound pressure level values measured at the basic microphone positions (dB difference between the highest and lowest sound pressure levels) exceeds twice the number of measurement points;
b) The noise radiated by the sound source is highly directional; c) A loud source whose noise radiates outward only through a small local area of the sound source, such as an opening of a pump that is enclosed in a circle. For a), the method for increasing the number of measurement points is as shown in Figure C1 in Appendix C, by increasing the number of rectangular unit areas of equal size.
For b) or c), use additional microphone positions in the high noise radiation area on the measurement surface (see 7.4.1). 7.4 Additional method for selecting microphone positions
7.4.1 Additional microphone positions on the measurement surface are selected according to 7.2.2 or 7.3.2. If additional microphone positions are required, a detailed investigation of the sound pressure level on a limited part of the measurement surface must be carried out. The purpose of the investigation is to determine the highest and lowest sound pressure levels within the frequency range of the test. The additional microphone positions are not connected with equal areas on the measurement surface. In this case, the calculation procedure of GB/T6882 (non-equal area) should be used to determine Lw. 7.4.2 Reducing microphone positions For special types of pumps, if the investigation shows that the surface sound pressure level measured after the number of microphone positions is reduced does not differ from the result measured with all microphone positions according to 7.2 and 7.3 by more than ±1dB, the number of microphone positions can be reduced. An example is a sound source with a symmetrical radiation pattern. Note 7: For safety reasons, the measurement points at the top of the sound source can be omitted. This should be noted in the corresponding noise test specification. 7.5 Measurement
7.5.1 Environmental conditions
When environmental conditions have an impact on the measuring microphone (e.g. strong electricity, magnetic field, wind, impact of air discharge of the equipment under test, high temperature or low temperature), the microphone should be appropriately selected or positioned to avoid it. The adverse environmental conditions indicated in the instruction manual of the measuring instrument should also be noted. 7.5.2 Measuring instrument
In addition to the provisions given in Chapter 5, the following requirements shall be met: a) The orientation of the microphone shall be the same as the sound wave incidence angle when it is calibrated. b) The time-averaged sound pressure level shall be measured using an integrating sound level meter that meets the requirements. When the sound pressure level fluctuation measured with the time characteristic s is less than ±1dB, a sound level meter that meets the requirements is allowed to be used. In the latter case, the average of the maximum and minimum sound pressure levels during the measurement period is used to represent the time-averaged sound pressure level.
7.5.3 Measurement method
Observe the A-weighted sound pressure level over a typical period of the sound source operation and read the A-weighted sound pressure level at each microphone position. Determine the following quantities: wwW.bzxz.Net
a) A-weighted sound pressure level L'PA of the sound source under test during operation b) A-weighted sound pressure level L\PA of the background noise. Unless otherwise specified in the special noise test specification, the observation period should be at least 30 s. For independent single sound events, measure the single event sound pressure level Lp.1s. For noise that changes with time, the observation period should be carefully specified. This is often related to the purpose of the measurement. For machines whose noise level changes with the change of working mode, an appropriate measurement period should be selected for each working mode and noted in the test report. 8 Calculation of A-weighted surface sound pressure level and A-weighted sound power level 8.1 Calculation of average A-weighted sound pressure level of the measurement surface The average A-weighted sound pressure level of the measurement surface and the average A-weighted sound pressure level of the background noise on the measurement surface are calculated using formula (4) and formula (5): L'pa (dB) = 10lg[
L\pA (dB) = 10lg
Where: LPA is the average A-weighted sound pressure level of the measurement surface during the operation of the measured sound source, dB; L\PA is the average A-weighted sound pressure level of the background noise on the measurement surface, dB; L'pA is the A-weighted sound pressure level measured at the i-th microphone position, dB; L\PA is the A-weighted sound pressure level of the background noise measured at the i-th microphone position, dB; N is the number of microphone positions.
Note 8: The averaging method of formula (4) and formula (5) is based on the premise that the microphone positions on the measurement surface are evenly distributed. 8.1.1 Background noise correction
Correction value K1A is calculated using formula (6):
KiA(dB) - - 10lg(1 -- 10-0.14LA)Where: ALA = L'PA — L\PA. If △LA>10dB, no correction is required; if △LA≥3dB, the measurement made in accordance with this standard is valid (see Table 0.1). ·(4)
·(5)
·(6)
JB/T8098—1999
When △LA is between 3dB and 10dB, it should be corrected according to formula (6). If △LA<3dB, the accuracy of the measurement result will be reduced. The maximum correction value that can be added to the measurement is 3dB. However, such measurement results can also be reported. It can be used as a reference for determining the upper limit sound power level of the measured sound source. When reporting, the failure of the background noise to meet the requirements of this standard shall be explained in detail in the text of the report and in the charts and tables of the results.
8.1.2 Test environment correction
The environmental correction K2A is determined by one of the methods given in Appendix A. When K2A≤7dB, the measurement made in accordance with this standard is valid (see Table 0.1).
8.1.3 Calculation of A-weighted surface sound pressure level
The surface sound pressure level LpA is calculated according to formula (7): LPA L'PA - KiA - K2A
8.2 Calculation of sound power level
The sound power level LwA is calculated according to formula (8):
LwA (dB) = LpA + 10lg!
Where: LPA - A-weighted surface sound pressure level; - Area of the measuring surface, m\;
S. - lm.
8.3 Determination of optional quantities
Special noise test specifications for the following optional noise sources may require: (7)
.(8))
a) data on the determination of impulse noise by the method of Appendix D (indicative appendix) and/or the presence of discrete pure tones determined by hearing; b) the sound pressure spectrum measured at a single microphone position on the surface or averaged over the surface; c) the variation of the A-weighted sound pressure level with time at a specified microphone position and the difference between the A-weighted sound pressure levels at different microphone positions on the surface;
d) the sound pressure level at different microphone positions on the surface with different time weightings and/or different frequency weightings. 9 Method for measuring the sound pressure level of pumps
9.1 Method for measuring the A-weighted sound pressure level
9.1.1 Location of measuring points
The selection of measuring points for representative pumps and prime movers (motors) is shown in Figures 2 to 8. The measuring points for other pumps and pump speed couplings can be determined by referring to this legend.
The horizontal distance between the measuring point and the surface of the pump body is 1m. The height of the measuring point is stipulated as follows:
The height of the pump axis from the sound reflection surface (ground) is the center height of the pump. When the center height of the pump is less than or equal to 1m, the height of the measuring point is stipulated as 1m. When the center height of the pump is greater than 1m, the height of the measuring point is the same as the center height. Refer to Figures 2 to 8. 9.1.2 Calculation of the measured value of the A sound pressure level and the average sound pressure value LrA Refer to Figures 2 to 8 according to the type of pump, specify the measuring points of the pump and the prime mover (motor), measure the A sound level reading value LpAi of the sound source at the specified measuring point, and correct it according to formula (6) against the background noise of each measuring point to obtain the measured value of the A sound level LpA-K1 of each measuring point; use formula (4) of this standard to calculate the average of the measuring points around the pump (P-1~~P-5) and the measuring points around the prime mover (M-1~M-3). When evaluating the noise of the pump, use the average value of the measuring points around the pump, and when evaluating the noise of the unit, use the total average value including all measuring points, both of which are expressed as LPA.
P-4 -0
M-1 d-
JB/T 8098--1999
Figure 2 Single-stage centrifugal pump
Figure 3 Two-stage centrifugal pump3 Measurement method
Observe the A-weighted sound pressure level during the typical period of the sound source operation and read the A-weighted sound pressure level at each microphone position. Determine the following quantities:
a) A-weighted sound pressure level L'PA during the operation of the sound source under test b) A-weighted sound pressure level L\PA of the background noise. Unless otherwise specified in the special noise test specification, the observation period should be at least 30 s. For independent single sound events, measure the single event sound pressure level Lp.1s. For noise that changes with time, the observation period should be carefully specified. This is often related to the purpose of the measurement. For machines whose noise level changes with the change of working mode, an appropriate measurement period should be selected for each working mode and noted in the test report. 8 Calculation of A-weighted surface sound pressure level and A-weighted sound power level 8.1 Calculation of average A-weighted sound pressure level of the measurement surface The average A-weighted sound pressure level of the measurement surface and the average A-weighted sound pressure level of the background noise on the measurement surface are calculated using formula (4) and formula (5): L'pa (dB) = 10lg[
L\pA (dB) = 10lg
Where: LPA is the average A-weighted sound pressure level of the measurement surface during the operation of the measured sound source, dB; L\PA is the average A-weighted sound pressure level of the background noise on the measurement surface, dB; L'pA is the A-weighted sound pressure level measured at the i-th microphone position, dB; L\PA is the A-weighted sound pressure level of the background noise measured at the i-th microphone position, dB; N is the number of microphone positions.
Note 8: The averaging method of formula (4) and formula (5) is based on the premise that the microphone positions on the measurement surface are evenly distributed. 8.1.1 Background noise correction
Correction value K1A is calculated using formula (6):
KiA(dB) - - 10lg(1 -- 10-0.14LA)Where: ALA = L'PA — L\PA. If △LA>10dB, no correction is required; if △LA≥3dB, the measurement made in accordance with this standard is valid (see Table 0.1). ·(4)
·(5)
·(6)
JB/T8098—1999
When △LA is between 3dB and 10dB, it should be corrected according to formula (6). If △LA<3dB, the accuracy of the measurement result will be reduced. The maximum correction value that can be added to the measurement is 3dB. However, such measurement results can also be reported. It can be used as a reference for determining the upper limit sound power level of the measured sound source. When reporting, the failure of the background noise to meet the requirements of this standard shall be explained in detail in the text of the report and in the charts and tables of the results.
8.1.2 Test environment correction
The environmental correction K2A is determined by one of the methods given in Appendix A. When K2A≤7dB, the measurement made in accordance with this standard is valid (see Table 0.1).
8.1.3 Calculation of A-weighted surface sound pressure level
The surface sound pressure level LpA is calculated according to formula (7): LPA L'PA - KiA - K2A
8.2 Calculation of sound power level
The sound power level LwA is calculated according to formula (8):
LwA (dB) = LpA + 10lg!
Where: LPA - A-weighted surface sound pressure level; - Area of the measuring surface, m\;
S. - lm.
8.3 Determination of optional quantities
Special noise test specifications for the following optional noise sources may require: (7)
.(8))
a) data on the determination of impulse noise by the method of Appendix D (indicative appendix) and/or the presence of discrete pure tones determined by hearing; b) the sound pressure spectrum measured at a single microphone position on the surface or averaged over the surface; c) the variation of the A-weighted sound pressure level with time at a specified microphone position and the difference between the A-weighted sound pressure levels at different microphone positions on the surface;
d) the sound pressure level at different microphone positions on the surface with different time weightings and/or different frequency weightings. 9 Method for measuring the sound pressure level of pumps
9.1 Method for measuring the A-weighted sound pressure level
9.1.1 Location of measuring points
The selection of measuring points for representative pumps and prime movers (motors) is shown in Figures 2 to 8. The measuring points for other pumps and pump speed couplings can be determined by referring to this legend.
The horizontal distance between the measuring point and the surface of the pump body is 1m. The height of the measuring point is stipulated as follows:
The height of the pump axis from the sound reflection surface (ground) is the center height of the pump. When the center height of the pump is less than or equal to 1m, the height of the measuring point is stipulated as 1m. When the center height of the pump is greater than 1m, the height of the measuring point is the same as the center height. Refer to Figures 2 to 8. 9.1.2 Calculation of the measured value of the A sound pressure level and the average sound pressure value LrA Refer to Figures 2 to 8 according to the type of pump, specify the measuring points of the pump and the prime mover (motor), measure the A sound level reading value LpAi of the sound source at the specified measuring point, and correct it according to formula (6) against the background noise of each measuring point to obtain the measured value of the A sound level LpA-K1 of each measuring point; use formula (4) of this standard to calculate the average of the measuring points around the pump (P-1~~P-5) and the measuring points around the prime mover (M-1~M-3). When evaluating the noise of the pump, use the average value of the measuring points around the pump, and when evaluating the noise of the unit, use the total average value including all measuring points, both of which are expressed as LPA.
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Figure 2 Single-stage centrifugal pump
Figure 3 Two-stage centrifugal pump3 Measurement method
Observe the A-weighted sound pressure level during the typical period of the sound source operation and read the A-weighted sound pressure level at each microphone position. Determine the following quantities:
a) A-weighted sound pressure level L'PA during the operation of the sound source under test b) A-weighted sound pressure level L\PA of the background noise. Unless otherwise specified in the special noise test specification, the observation period should be at least 30 s. For independent single sound events, measure the single event sound pressure level Lp.1s. For noise that changes with time, the observation period should be carefully specified. This is often related to the purpose of the measurement. For machines whose noise level changes with the change of working mode, an appropriate measurement period should be selected for each working mode and noted in the test report. 8 Calculation of A-weighted surface sound pressure level and A-weighted sound power level 8.1 Calculation of average A-weighted sound pressure level of the measurement surface The average A-weighted sound pressure level of the measurement surface and the average A-weighted sound pressure level of the background noise of the measurement surface are calculated using formula (4) and formula (5): L'pa (dB) = 10lg[
L\pA (dB) = 10lg
Where: LPA is the average A-weighted sound pressure level of the measurement surface during the operation of the measured sound source, dB; L\PA is the average A-weighted sound pressure level of the background noise of the measurement surface, dB; L'pA is the A-weighted sound pressure level measured at the i-th microphone position, dB; L\PA is the A-weighted sound pressure level of the background noise measured at the i-th microphone position, dB; N is the number of microphone positions.
Note 8: The averaging method of formula (4) and formula (5) is based on the premise that the microphone positions on the measurement surface are evenly distributed. 8.1.1 Background noise correction
Correction value K1A is calculated using formula (6):
KiA(dB) - - 10lg(1 -- 10-0.14LA) Where: ALA = L'PA — L\PA. If △LA>10dB, no correction is required; if △LA≥3dB, the measurement made in accordance with this standard is valid (see Table 0.1). · (4)
· (5)
· (6)
JB/T8098—1999
When △LA is between 3dB and 10dB, it should be corrected according to formula (6). If △LA<3dB, the accuracy of the measurement result will be reduced. The maximum correction value that can be added to the measurement is 3dB. However, such measurement results can also be reported. It can be used as a reference for determining the upper limit sound power level of the measured sound source. When reporting, the failure of the background noise to meet the requirements of this standard shall be explained in detail in the text of the report and in the charts and tables of the results.
8.1.2 Test environment correction
The environmental correction K2A is determined by one of the methods given in Appendix A. When K2A≤7dB, the measurement made in accordance with this standard is valid (see Table 0.1).
8.1.3 Calculation of A-weighted surface sound pressure level
The surface sound pressure level LpA is calculated according to formula (7): LPA L'PA - KiA - K2A
8.2 Calculation of sound power level
The sound power level LwA is calculated according to formula (8):
LwA (dB) = LpA + 10lg!
Where: LPA - A-weighted surface sound pressure level; - Area of the measuring surface, m\;
S. - lm.
8.3 Determination of optional quantities
Special noise test specifications for the following optional noise sources may require: (7)
.(8))
a) Data on the determination of impulse noise in accordance with the method of Appendix D (indicative appendix) and/or the presence of discrete pure tones determined by hearing; b) The sound pressure spectrum measured at a single microphone position on the surface or averaged over the surface; c) The variation with time of the A-weighted sound pressure level at a specified microphone position and the difference between the A-weighted sound pressure levels at different microphone positions on the surface;
d) The sound pressure levels at different microphone positions on the surface with different time weightings and/or different frequency weightings. 9 Method for measuring the sound pressure level of pumps
9.1 Method for measuring the A-weighted sound pressure level
9.1.1 Location of measuring points
The selection of measuring points for representative pumps and prime movers (motors) is shown in Figures 2 to 8. The measuring points for other pumps and pump speed couplings can be determined by referring to this legend.
The horizontal distance between the measuring point and the surface of the pump body is 1m. The height of the measuring point is stipulated as follows:
The height of the pump axis from the sound reflection surface (ground) is the center height of the pump. When the center height of the pump is less than or equal to 1m, the height of the measuring point is stipulated as 1m. When the center height of the pump is greater than 1m, the height of the measuring point is the same as the center height. Refer to Figures 2 to 8. 9.1.2 Calculation of the measured value of the A sound pressure level and the average sound pressure value LrA Refer to Figures 2 to 8 according to the type of pump, specify the measuring points of the pump and the prime mover (motor), measure the A sound level reading value LpAi of the sound source at the specified measuring point, and correct it according to formula (6) against the background noise of each measuring point to obtain the measured value of the A sound level LpA-K1 of each measuring point; use formula (4) of this standard to calculate the average of the measuring points around the pump (P-1~~P-5) and the measuring points around the prime mover (M-1~M-3). When evaluating the noise of the pump, use the average value of the measuring points around the pump, and when evaluating the unit noise, use the total average value including all measuring points, both of which are expressed as LPA.
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Figure 2 Single-stage centrifugal pump
Figure 3 Two-stage centrifugal pump(8) a) Determine the data of impulse noise according to the method of Appendix D (suggested Appendix) and/or determine the presence of discrete pure tones by hearing; b) Measure the sound pressure spectrum of a single microphone position on the surface or the average sound pressure spectrum on the surface; c) Change the A-weighted sound pressure level with time at a specified microphone position and measure the difference between the A-weighted sound pressure levels at different microphone positions on the surface; d) Measure the sound pressure level of each microphone position on the surface with different time weighting and/or different frequency weighting. 9 Method for measuring the sound pressure level of pumps 9.1 Method for measuring the A-weighted sound pressure level 9.1.1 Measurement point location The selection of representative measurement points for pumps and prime movers (motors) is shown in Figures 2 to 8. The measurement points of other pumps and pump speed couplings can be determined by referring to this legend. The horizontal distance between the measurement point and the pump body surface is 1m. The height of the measuring point is defined as follows:
The height of the pump axis from the sound reflection surface (ground) is the center height of the pump. When the center height of the pump is less than or equal to 1m, the measuring point height is defined as 1m. When the center height of the pump is greater than 1m, the measuring point height is the same as the center height. Refer to Figures 2 to 8. 9.1.2 Calculation of the measured value of the A sound pressure level and the average sound pressure value LrA Refer to Figures 2 to 8 according to the type of pump, specify the measuring points of the pump and the prime mover (motor), measure the A sound level reading value LpAi of the sound source at the specified measuring point, and correct it according to formula (6) against the background noise of each measuring point to obtain the measured value of the A sound level LpA-K1 of each measuring point; use formula (4) of this standard to calculate the average of the measuring points around the pump (P-1~~P-5) and the measuring points around the prime mover (M-1~M-3). When evaluating the noise of the pump, use the average value of the measuring points around the pump, and when evaluating the noise of the unit, use the total average value including all measuring points, both of which are expressed as LPA.
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JB/T 8098--1999
Figure 2 Single-stage centrifugal pump
Figure 3 Two-stage centrifugal pump(8) a) Determine the data of impulse noise according to the method of Appendix D (suggested Appendix) and/or determine the presence of discrete pure tones by hearing; b) Measure the sound pressure spectrum of a single microphone position on the surface or the average sound pressure spectrum on the surface; c) Change the A-weighted sound pressure level with time at a specified microphone position and measure the difference between the A-weighted sound pressure levels at different microphone positions on the surface; d) Measure the sound pressure level of each microphone position on the surface with different time weighting and/or different frequency weighting. 9 Method for measuring the sound pressure level of pumps 9.1 Method for measuring the A-weighted sound pressure level 9.1.1 Measurement point location The selection of representative measurement points for pumps and prime movers (motors) is shown in Figures 2 to 8. The measurement points of other pumps and pump speed couplings can be determined by referring to this legend. The horizontal distance between the measurement point and the pump body surface is 1m. The height of the measuring point is defined as follows:
The height of the pump axis from the sound reflection surface (ground) is the center height of the pump. When the center height of the pump is less than or equal to 1m, the measuring point height is defined as 1m. When the center height of the pump is greater than 1m, the measuring point height is the same as the center height. Refer to Figures 2 to 8. 9.1.2 Calculation of the measured value of the A sound pressure level and the average sound pressure value LrA Refer to Figures 2 to 8 according to the type of pump, specify the measuring points of the pump and the prime mover (motor), measure the A sound level reading value LpAi of the sound source at the specified measuring point, and correct it according to formula (6) against the background noise of each measuring point to obtain the measured value of the A sound level LpA-K1 of each measuring point; use formula (4) of this standard to calculate the average of the measuring points around the pump (P-1~~P-5) and the measuring points around the prime mover (M-1~M-3). When evaluating the noise of the pump, use the average value of the measuring points around the pump, and when evaluating the noise of the unit, use the total average value including all measuring points, both of which are expressed as LPA.
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Figure 2 Single-stage centrifugal pump
Figure 3 Two-stage centrifugal pump
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