This standard specifies the measurement method of the sound intensity component perpendicular to the measurement surface. The measurement surface should surround the noise source to be measured. This method is applicable to any sound source with a defined measurement surface. GB/T 16404-1996 Acoustics Determination of sound power level of noise source by sound intensity method Part 1: Measurement at discrete points GB/T16404-1996 Standard download decompression password: www.bzxz.net
This standard specifies the measurement method of the sound intensity component perpendicular to the measurement surface. The measurement surface should surround the noise source to be measured. This method is applicable to any sound source with a defined measurement surface.

GB/T 16404—1996
This standard is formulated based on the international standard [ISO9614-1:1993 Acoustics—Determination of sound power level of noise sources by the sound intensity method—Part 1: Measurement at discrete points]. This standard is equivalent to the international standard ISO9611-1:1993. This standard has made appropriate modifications to some of the provisions of the international standard according to the specific situation in my country. This standard shall be implemented from December 1, 1996. Appendix A and Appendix B of this standard are standard appendices. Appendix C and Appendix D of this standard are suggested appendices. Since Appendix E suggested in ISO9614-1 is a reference, it is omitted in this standard. This standard is proposed and managed by the National Technical Committee for Acoustic Standardization. The drafting units of this standard are: Institute of Acoustics, Chinese Academy of Sciences, Hefei University of Technology, Shanghai Institute of Electrical Science. The main drafters of this standard are: Cheng Mingkun, Chen Xinzhao and Chen Yeshao. GB/T 164041996
ISO Foreword
ISU (International Organization for Standardization) is composed of standardization organizations of countries around the world (ISO member countries). The main task of ISO technical committees is to draft international standards. Each member country interested in the standards drafted by the technical committee has the right to express its opinions to the committee. International organizations related to ISO (whether governmental or non-governmental) can participate in the work of standard formulation. ISO has a close working relationship with the International Electrotechnical Commission F in all aspects of electrical standards. The draft international standards adopted by the technical committee are submitted to the member countries for voting. At least 75 voting countries must approve them before they can be published as formal international standards.
International standard ISO 9614-1 is provided by the noise subcommittee SC1 of the ISO/TC43 acoustics committee. The general title of ISO 9614 is acoustics-determination of the sound frequency level of noise sources by the sound intensity method. It consists of two parts:
Part 1: Measurement at discrete points
Part 2: Scanning measurement
Appendix A and Appendix B constitute the complete part of this standard, and Appendix C, Appendix D and Appendix E are only for reference. CB/T 164041996
0.1The sound power radiated by a sound source is equal to the integral of the scalar product of the sound intensity vector and the corresponding surface element vector on any surface surrounding the sound source. At present, the national standards for the measurement of sound power level of noise sources, such as GB3767.GB3768.GI36881, GH6882, etc., all use sound pressure level as the basic quantity for measurement. The relationship between the sound intensity level and the sound pressure level at any point depends on the characteristics of the sound source, the characteristics of the measurement environment, and the configuration of the measurement point relative to the sound source. Therefore, the above national standards must not only ensure that the sound power level measurement meets the specified uncertainty, but also specify the characteristics of the sound source, the characteristics of the test environment, and the conditions of use restrictions. However, the methods specified in national standards such as GB3767 are sometimes not applicable, such as 1a) If high-precision measurements are required, special facilities (such as reverberation chambers, anechoic chambers, and semi-anechoic chambers) are required, and human-type equipment is often unable to be installed and operated in such facilities. b) The sound level of noise generated by other sound sources is too high. The purpose of this standard is to specify a method for determining the sound power level of a sound source within a specified uncertainty range and not subject to the test conditions of standards such as GB3767.
The sound power measured by this standard method is the sound power at the scene. In fact, it is a function of the environment, so in some cases it will be different from the sound power measured by other methods.
0.2 This standard is a supplement to GB3767, GB3768, GB6881, and GB6882. The differences from these national standards are: a) The basic measurement is sound intensity.
) The uncertainty of the sound power level measured by the method specified in this standard is classified according to the auxiliary tests and calculation results specified in the standard.
e) Due to the limitations of current sound intensity measurement equipment, the 1/3 octave measurement frequency range is limited to 50 Hz to 6.3 kHz. The A-weighting is determined based on the 1/1 or 1/3 octave band sound pressure level, not directly measured. 0.3 This standard specifies a method for determining the sound power level of a steady-state noise source using the sound intensity on the measurement surface containing the sound source. In principle, the sound power measured in this way gives the sum of the sound powers directly radiated into the air by all sound sources within the measurement surface. It does not include the sound radiation from sound sources outside the surface. When there are other sound sources outside the measurement surface, any system with sound absorption characteristics within the surface will absorb part of the energy incident on it, and the total sound power absorbed within the measurement surface will be negative and will cause errors in the sound power determination; therefore, in order to minimize errors, any sound absorbing materials within the measurement surface must be moved. This standard is based on discrete point sampling of the sound intensity field perpendicular to the measurement surface. The sampling error is a function of the spatial variation of the normal sound intensity on the measurement surface and depends on the directivity of the sound sources, the chosen sampling surface, the distribution of the sampling points and the proximity of the sources to the measurement surface. The accuracy of the measurement of the normal component of the sound intensity at a measurement point is closely related to the difference between the local sound pressure level and the local normal sound intensity level, which becomes very large when the angle between the sound intensity at a measurement point and the normal direction of the measurement surface element approaches 90°. In other words, the sound pressure level mainly comes from sound sources outside the measurement surface and has little to do with the pure sound energy flow of the measured sound source, like the reverberant field in a condenser; or the sound field is strongly resistive due to the presence of near fields and/or standing waves. National Standard of the People's Republic of China
Acoustics-Determination of sound power levelsof noise sources using sound intensityPart 1.Measurement at discrete points1 Scope
GB/T 16404-1996
eqy Is0 9614-1:1993
1.1 This standard specifies the method for measuring the sound intensity component perpendicular to the measurement surface. The measurement surface should surround the noise source to be measured. The weighted sound power level of 1/1, 1/3 octave band or other bandwidth is calculated based on the measured values. This method is applicable to any sound source with a defined measurement surface. On the measurement surface, the noise generated by the sound source is steady in time (see definition in 3.13). The measurement surface is selected according to the size and shape of the sound source. This method can be used in the field to destroy the test environment for special purposes. 1.2 This standard can be used for sound sources in any environment where the ambient environment does not change over time in such a way that the accuracy of the sound intensity measurement is unacceptable or where the sound intensity measuring probe is not affected by high-speed or unstable air (see 5.3 and 5.4). Test conditions may not always meet the requirements of this standard, especially when the external noise level changes greatly during the test. The method given in this standard is not suitable for determining the sound power level of the sound source. NOTE 1 Other methods, such as the method of determining the sound power level by
surface vibration level specified in GB/T 16529-1996 Acoustics: Determination of the sound power level of noise sources by the vibration inversion method for the measurement of enclosed machines, may be more appropriate. 1.3 This standard specifies an auxiliary method for judging the quality of the measurement, i.e. the level of accuracy. It is listed in the appendix. If the results obtained by this method show that the measurement accuracy does not meet the requirements of this standard, the test procedure should be modified in accordance with Appendix B. 2 Referenced standards
The texts contained in the following standards constitute the provisions of this standard through the use of the numbers in this standard: At the time of publication of the standard, the versions indicated are valid. All standards are subject to revision, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T15173-1994, Sound calibrator (eqvIEC942:1988) TSO5725:1986, Accuracy of test methods-Determination of repeatability and reproducibility of a standard test method by the exchange laboratory test method
IFC1043:1993, Electroacoustics Sound intensity measurement instrument using paired sound pressure microphones for measurement 3 Definitions
This standard adopts the following definitions:
3.1 Sound pressure level (L,) sound pressure level is 20 times the logarithm of the ratio of sound pressure to the reference sound pressure with the base 10, the reference sound pressure is 20μPa, and the sound pressure level is expressed in decibels, with the symbol dB. 3.2 Instantaneous sound intensity (i(t)) instantaneous sound intensity is the sound energy per unit area in a certain point in the sound field that passes through the direction of the particle velocity in a unit time. The instantaneous sound intensity at a certain point in the sound field is a vector, which is equal to the product of the instantaneous sound pressure at that point and the instantaneous particle velocity. Approved by the State Administration of Technical Supervision on May 27, 1996, and implemented on December 1, 1996
In the formula: I(t) is the instantaneous sound intensity,W/m
Instantaneous sound pressure, Pa/m\;
u(t) Instantaneous particle velocity, m/s.
3.3 Sound intensity (1) sound intensity
GB/T 16404—1996
I(r) - (t) +u()
The average value of the instantaneous sound intensity I(t) in a steady-state sound field within a certain time T: 1=
Wherein, T is an integer multiple of a period or a time long enough not to affect the calculation result, "is the amplitude of the vector I, which may be positive or negative, depending on the propagation direction of the sound energy flow of the measured sound source; I is the absolute value of the vector amplitude.
3.4 ​​Normal sound intensity I, normal spunt intensityThe sound component perpendicular to the measurement surface defined by the unit normal vector n I=In
The unit normal vector pointing to the outside of the measurement surface.
3.5 Normal sound intensity level (L)normalsoundintensitylevelThe unsigned value of the normal sound intensity|1. "The logarithm of the quantity, expressed as follows; L =- 10 lg(,//,.
The unit is decibel, where I. is the reference sound intensity (=10-12W/m*), unless used for the calculation of 8p, when I. is sufficient, the sound intensity level is expressed as (-)××dB (see 3.11). 3.6 Sound power saunrl power
3.6.1 Partial sound power (W,) The sound power passing through a measurement surface element, the unit is watt, the derivative symbol is W, it is expressed as follows: W,=ls.=Iμ-s.
Where; 1.-The normal sound intensity amplitude measured at a point on the measurement surface; S:-"The area of ​​the measurement surface element corresponding to the principal point. 3.6.2 Lu power (W) sound pawer
The total sound power radiated by a sound source measured according to the standard. It is given by equations (6) and (7): W
Formula: N-the total number of measurement elements.
3.6.3 Sound power level (Lw) soundpowerlevelSw
The logarithm of the sound power of a sound source measured according to the standard, which is given by the following equation: Lu(dR)-10lgC/W/W.)
The amplitude of the sound power of a sound source;
W. —reference sound power (-10-W)n
The sound power level is expressed in decibels, with the symbol dB. When W is a negative value, the sound power level is (-)××dB, which is only used for recording. Note 2: If it is found that the W value is negative, this standard cannot be used. 3.7 Measurement surface meaguremcnt surface (5)
The imaginary surface on which the sound intensity measurement is carried out, which either completely surrounds the noise source to be measured or, in conjunction with an acoustically rigid continuous surface, surrounds the noise source to be measured: if the imaginary surface contains a rigid hard surface, the measurement surface shall be deducted from the hard surface portion. 3.8 Segment
The measurement surface corresponding to a measuring point.
3.9 Extraneous intensity The sound intensity component caused by a sound source outside the measurement attenuation surface. 3.10 Probe
The part of the sound measurement system with the sensor. 3.11 Pressure-residual intensity index p. Pressure-residual intensity index pl, the difference between the sound pressure level L, and the sound intensity level L, expressed in decibels, when the sound intensity probe is placed in the sound field with its axis along the direction where the sound intensity is equal to 0.
IEC1043 gives a detailed method for determining 8p., where the subscript "" indicates the direction of the probe axis. r, = (L, - Im)
3.12 Dynamic Capability Index (La) dynamic capahility index It is given by equation (10):
L = p, Kbzxz.net
Expressed in decibels (dB),
The deviation factor K is selected according to the accuracy requirements (see Table 1). Table 1
Accuracy
(Grade 1)
(Grade 2)
(Grade 3)
3.13 Stationary signal deviation, dE
A signal is considered to be stationary if the time-averaged characteristic of each individual measurement point is equal to the time-averaged characteristic of the same measurement point measured using the total time spent measuring all the measurement points on the measurement surface. According to this definition, a periodic signal can be considered as steady-state if the measurement time for a period of more than 10 fixed periods at a measuring point is greater than 10 fixed periods. 3.14 Sound field indicator aF, toF See Appendix A.
4 General requirements
4.1 Size of noise source
The size of the noise source is not limited, and the measurement surface depends on the size of the sound source. 4.2 Noise characteristics of the sound source
As defined in 3.13, the signal should be steady-state in time. If a sound source operates according to an operating cycle, during which there are obvious continuous stable operation time periods, the sound power level of each obvious time period should be determined and reported. If the external noise source is non-stable, measurements should be avoided before necessary measures are taken. (See Table B, 3 of Appendix B). 4.3 Uncertainty of measurement
Three accuracy levels are specified in Table 2. The uncertainty takes into account the random error related to the measurement process and the maximum measurement deviation, which is related to the choice of K value. K corresponds to the required accuracy. The tolerance of instrument performance specified in 1HC1743 is not considered here, nor is the influence of changes in the installation, fixing and operating conditions of the sound source considered. There is currently insufficient data to determine the value of uncertainty below 50 Hz. Therefore, the frequency range of A-weighting is 63 Hz to 4 kHz for the 1/1 octave band and 50 Hz to 6.3 kHz for the 1/3 octave band. If there is no obvious high GB/T 16404-1996
sound level in the frequency range below 50 Hz and above 6.3 kHz, then the A-weighted sound power value calculated from the 1/1 octave band from 63 Hz to 4 kHz and the 1/3 octave band from 50 Hz to 6.3 kHz is correct. The method to determine whether the sound pressure level of the frequency band outside 50 Hz to 6.3 kHz is to A-weight this frequency band. If its sound level is not lower than - dB of the total A-weighted value calculated according to the above peak frequency range, then the sound pressure level of this frequency band is obvious. If the A-weighted measurements and the corresponding sound power level determinations are made over a narrower frequency band, then this range shall be specified in accordance with (10.5b). Table 2 Uncertainties in sound power level determinations
1/1 octave band centre frequency
63 to 125
250 to 500
1 000 to 4 000
A-weighted
1/3 octave band centre frequency
50 to 160
200 to 630
800 to 5 000
Precision (Class 1)
1) The true value of the sound power level shall be determined with 95 % certainty within the ±2S range2) 63 Hz to -4 kHz or 50 Hz to 6.3 kHz. 3) Due to the wide variety of equipment that is suitable for this standard, the values ​​in this table are standard deviations for trial use. 51)
Engineering (2)
Simple (Level 3)
·The uncertainty in the measurement of the sound power level of a noise source is related to the sound field characteristics of the sound source, the characteristics of the external sound field, the sound absorption of the measured sound source, and the type of sound intensity field sampling and measurement method used. For this reason, the standard specifies the initial process for calculating the indicated value of the sound field characteristics of the measuring surface area (see Appendix A). Using this preliminary test result, select an appropriate treatment measure according to Tables B.2 and B.3 (see Appendix B). If only the A-weighted value needs to be measured, any weighted frequency band sound power level that is more than 10 dB lower than the highest A-weighted frequency band sound power level can be ignored. If more than one A-weighted cheek band sound power level is not significant, it can be ignored as long as the sum of their A-weighted sound power levels is more than 10 dB lower than the highest A-weighted frequency band sound power level: If only the total sound power level of frequency weighting is required, the uncertainty of any frequency band weighted sound power level that is more than 10 dB lower than the total weighted sound power level has no effect on the measurement. 5 Acoustic environment
5.1 Evaluation criteria for the adequacy of the test environment
The test environment should be sufficient to ensure that the principle of measuring the primary sound intensity using the measuring instruments specified in 1EC1043 is valid. In addition, it should meet the requirements of 5.2 to 5.4.
5.2 External sound intensity
5.2.1 External sound intensity level
Efforts should be made to reduce the external sound intensity level to ensure that the accuracy of the measurement is not reduced to an unacceptable level (see Appendix B and A2.2 of Appendix A).
Note 3: If a considerable part of the sound source being measured is sound-absorbing material, then high external sound intensity can lead to errors in the sound power calculation. Appendix D gives a method for calculating the error caused by external sound intensity in the special case of turning off the sound source being measured. 5.2.2 Variability of external noise
It should be ensured that changes in the intensity of external noise do not cause the time variation indication value F of the sound field to exceed the limit (see Table B.3). 5.3 Wind, airflow, vibration and temperature
When the airflow conditions near the sound intensity probe exceed the limits specified by the manufacturer for a good test of the measurement system, the measurement should be stopped. If there is no data on this, the measurement should be stopped when the average air velocity exceeds 2m/s (see Appendix C). When measuring outdoors, the probe wind shield must be used. The probe should not be placed in or close to any air flow with an average velocity exceeding 2m/s, and the probe should be fixed to avoid significant vibration.
Because the wind speed fluctuates around an average value, the measured acoustic dynamic level will be too high when the wind speed is close to the maximum allowable value. GB/T 164041996
5 If the temperature of the object is significantly different from the ambient air, the probe should be at least 20mm away from the object. If the temperature of the measured point is much higher than the ambient temperature, especially when there is a high temperature gradient across the probe, the probe should be avoided. 6 Air pressure and temperature affect air density and sound velocity. The influence of these quantities on the calibration of the instrument should be ascertained and appropriate corrections should be made (see IEC 1043).
5.4 Environmental conditions
During the test, the conditions of the test environment should remain as constant as possible. This is particularly important for sound sources with pure tone characteristics. If testing is necessary, the repeatability of the results should be checked (as specified in ISO 5725) and changes in the test environment should be recorded. It should be ensured that the operator does not stand on or near the axis of the probe when measuring at any measuring point. If possible: unnecessary objects should be removed from the vicinity of the sound source.
6 Instruments
6.1 General
Sound intensity measuring instruments and probes that meet the requirements of IEC 1043 should be used. Class 1 instruments should be used for determinations of Class 1 and Class 2. The pressure and temperature of the ambient air should be taken into account when adjusting the instrument in accordance with IEC 1043. The sound pressure residual sound intensity index of the measuring instrument for each measuring frequency band should be recorded in accordance with the standard.
6.2 Calibration and field verification
The instrument and probe shall comply with the requirements of IEC1043. The instrument shall be calibrated in accordance with national standards at least once a year to verify compliance with IEC1043 and the results shall be recorded in accordance with 10.3. Before each splash test, the instrument shall be checked using the field inspection procedures specified by the country. If the field inspection is not specified, the procedures given in 6.2.1 and 6.2.2 shall be carried out to find abnormal conditions in the measurement system. 6.2.1 Sound pressure level
Use a calibrator of level 0 and level 1 or level 1L in accordance with GB/T15173 to check the sound pressure level of each microphone of the sound intensity probe. 6.2.2 Sound intensity
Place the sound intensity probe at a point with high sound intensity on the measurement surface. The axis of the probe is perpendicular to the surface and the normal sound arc is measured (see 3.5). Rotate the sound intensity probe 180° (i.e. turn the probe upside down) and keep its acoustic center at the same position as the first measurement before measuring the sound intensity. It is best to fix the sound intensity probe on a bracket so that the position remains unchanged when the probe is rotated. The values ​​of the two maximum cheek-band sound intensity levels I, measured using the 1/1 octave band or the 1/3 octave band should be opposite. If the difference between their sound intensity levels is less than 1.5 dB, the measuring instrument is considered acceptable.
7 Installation and operation of sound sources
7.1 General
The sound source shall be installed in a manner representative of normal use or in a manner specified in the test specification for a special type of machine or equipment.
7.2 Operating and installation conditions of the sound source during testing For special types of machines or equipment, the operating and installation conditions specified in the test specification shall apply. If there is no test specification, the sound source shall be operated under load in a steady-state condition representative of normal use. The following operating conditions can be selected:
a) Under the load representing the maximum sound produced in normal use (the probability of such use is less than 10%); b) Under full load conditions;
c) Under no load conditions (no load);
d) Under simulated load conditions (loads that do not represent normal use, but are likely to be the loads that produce the most human sound); ) Other specified load and operating conditions. It is recommended to use a) or b> as the main operating conditions, and the others can be selected as additional operating conditions. 8 Measurement of normal sound intensity level components
8.1 Averaging time
CB/T 16404—1996
If the maximum error of the sound intensity measurement is 5% with a confidence level of 95%, the averaging time of the instrument equipped with a filter for Gaussian white noise should meet
BT 400
Wu Zhong: B—Filter bandwidth
T averaging time.
For instruments that synthesize 1/1 or 1/3 octave bands from case band analysis, the equivalent averaging time or number should be selected in accordance with EC 1043. Special attention should be paid to shield signals.
8.2 Preliminary test
The normal sound intensity measurement should be carried out on an initial measurement surface. If the measurement results show that this initial measurement surface does not meet the requirements, it should be corrected according to the measures specified in Appendix B. The initial measurement surface should surround the sound source to be measured. NOTE? : It is best to take a measurement surface with a simple geometry and similar shape to the sound source to be measured, as shown in Figure 1. Parallel six
Optional initial measurement surface in Figure 1
Semi-cylindrical
The average separation between the measurement surface and the sound source surface should generally be greater than 0.5m. Unless the surface to be measured is located in a machine part with low sound radiation and little effect on the sound power of the measured sound source, or the measured sound source is very small, the selected measurement surface may include non-sound absorbing surfaces (diffuse sound field absorption coefficient less than 0.06) such as concrete floors or masonry walls. Sound arc measurements should not be made on such surfaces. Such surface areas are not included in the calculation of sound power according to the formula (see 3.6.2). In order to evaluate whether the sound field is steady, a "typical" measurement position should be selected on the initial measurement surface and the indicated value F for all measurement frequency bands should be calculated according to A2.1 of Appendix A. If the time variation of the sound field exceeds the value specified in Table B3 of Appendix B, appropriate measures should be taken according to Table B3 to reduce this variation.
If the A-weighted sound suffix measured at 5 measurement points with the measured sound source turned off is reduced by more than 10 dB, the external noise is considered to have no effect on the measurement. These 5 measurement points should be evenly distributed on the measurement surface. Jiang 8: If the sound source is turned off and the sound source with obvious noise outside the test surface is also turned off at the same time, then this method cannot be used to judge the influence of external noise.
In the sound power measurement, it is required to measure the normal sound intensity level and sound pressure level of each frequency band, with at least one measuring point per square meter and at least 10 measuring points on the entire measurement surface. They should be distributed as evenly as possible on the surface. If the external noise is obvious, more than 50 measuring points are required. As long as the total number of measuring points is not less than 50, it is allowed to reduce to one measuring point every 2m. If the external noise is not obvious and the measurement surface is greater than 50m, then 5 measuring points can be taken on the measurement surface, but they should be as evenly distributed as possible. According to Appendix A, calculate the sound field indication values ​​F..F. and F for all measurement bands, and substitute these values ​​into the formula of the qualified judgment method in B1.1. If this test is successful for each frequency band, the initial sound power determination is the final result, and its measurement uncertainty is within the range given in Table 2.
If none of the measured frequency bands meet the criteria of B., then one of the following measures must be taken:) According to 10.5, explain in the report the impact of the uncertainty of the sound power level in these frequency bands being greater than the accuracy level specified in Table 2.
GB/T 16404—1996
b) Take complementary measures to improve the accuracy of the measurement according to Table B3. If the criteria of B1.2 are not met for all frequency bands, then corresponding measures must be taken in accordance with 8.3 or 8.4. 8.3 Selection method with the least number of measurement points on the initial measurement surface 8.3.1 Identification of local sound power concentrations
If the test according to B1.2 (criterion 2) shows that for any frequency band, the normalized standard deviation F of the normal sound intensity measured on the initial measurement surface is less than the normalized standard deviation necessary to ensure that the sampling error is within the required accuracy level, then the normal sound intensity sampling process can be optimized and the array of measurement points can be selectively modified to minimize the additional measurement required to meet the test requirements of the initial measurement surface. The possibility of optimization can be tested by the method of 8.3.2: 8.3.2 Local sound power concentrations
This method confirms whether it is possible to optimize the normal sound intensity sampling process by modifying the array of measurement points. If criterion 1 of B1.1 is met and criterion 2 of B1.2 is not met, and in some or all of the measurement frequency bands F, -F, ≤ 1B, then most of the sound power in these frequency bands is likely to be transmitted through a subset of measurement bins whose total area is less than half the total area of ​​the measurement surface. If there is a local sound power concentration, then please use the calculation method specified in B1.3 to estimate the number of measurement points that need to be added to the subset. At the same time, the newly added measurement points should be distributed as evenly as possible on the surface (based on the subset area). Measure the normal sound intensity level of the newly added measurement points, and calculate the sound power and sound power level on the subset surface according to formulas (11) and (12). The sound power measured after correction is the final result, and its measurement uncertainty is within the range given in Table 2. If this selective correction process cannot be achieved, please take appropriate measures according to B2 and B3. 8.4 Further testing
If the inspection of B1 shows that the initially selected measurement point array or the measurement point array modified according to the process of 8.3.2 does not meet the required accuracy, then take measures according to B2. The modified measurement surface and measurement point array should be used to measure the normal sound intensity level components and the corresponding sound pressure levels, and recalculate the sound field indication values ​​F, F, and F. They should be evaluated according to B1 and measures should be taken according to B2. Repeat this process until the required accuracy is achieved. In case the repeated corrections do not satisfy the specified criteria, please record an invalid test result and explain the relevant reasons.
9 Calculation of sound power level
9.1 Calculate the local sound power for each element on the measurement surface. The local sound power W=Is
of each frequency band of each surface is calculated according to the following formula (11), where: W, is the local sound power of the surface element,
is the signed amplitude of the normal sound intensity component measured at the measuring point 1, and S, is the area of ​​the surface element.
When the normal sound intensity level Lm of the surface element is expressed as ××dB, the value of I is calculated according to the following formula: I =I.× 10w/15
When the normal sound intensity level La of the surface element i is expressed as (-)××dB, the value of 1 is calculated according to the following formula: I±-1.X10u/1g
where: 1, =10-13W/m
9.2 Calculation of noise source sound power level
The noise source sound power level of each frequency band is calculated according to formula (12): Lu(alB) = 10lg ZW,/W.
Where: W: local sound power of surface element i: W,——Chia sound power (=10-13W) #N—the total number of measurement points or surface elements.
***(12))
If
>W. of any frequency band is a negative value, the method of this standard is not applicable to this frequency band. When measuring according to this standard, the following contents should be collected and recorded. 10.1 Sound source to be measured
) Description of the sound source to be measured (including its size and surface characteristics). h) Characteristics of the sound source to be measured (variability, occurrence of periodicity, pure sound quality, etc.). c) Operating conditions.
d) Installation conditions.
10.2 Acoustic environment
a) Description of the test environment, including a sketch of the shell source position , shape and location of nearby objects, local topography and/or ground characteristics).
h) Description of the noise characteristics of the non-test sound source, including variability, occurrence of periods, and pure tone quality. c) Air temperature and static pressure.
d) Average wind speed and direction.
) Description of any equipment/methods used to minimize the effects of external noise. f) Qualitative description of any gas/air currents and instabilities. 10.3 Only
a) Equipment used for measurement, including name, model, serial number, manufacturer and probe configuration. b) Methods used for instrument calibration and field checks, including date of acquisition. c) Sound pressure residual intensity index for each band of the sound intensity measurement system when using different probe configurations. d) Date and location of calibration of the sound intensity measurement equipment. 10.4 Measurement Procedure
a) Description of each step of the measurement procedure.
b) Description of the probe fixing or support system during measurement. ) Quantitative description of the measurement surface and elements; a sketch should be provided. d) Description of the measurement array, giving the number and coordinates of each measuring point. c) Average time for each measuring point.
10.5 Scientific data
a) Table of sound field indication values ​​calculated for each set of measurements on each measuring surface of the saw. h) Graph or chart of calculated sound power levels in all frequency bands. Where an A-weighted sound power level is to be determined, the components of the bands that do not meet criteria 1 and/or 2 of Appendix B shall be omitted with an explanation of the effect of the omission, unless these components are negligible according to 4.3.
c) Explanation of the uncertainty of the sound power level in each frequency band measured by formula (B.3) that does not meet criterion 2 of Appendix B.
6.2.2 Description of the results of the field test in the reverse direction of the probe. e) Date of measurement (year/month/day)
6 Accuracy level of sound power level determination
The accuracy level of the final test shall be stated in accordance with Table 2. In special cases, when a certain test accuracy level can only be achieved within a limited frequency band, the 95% confidence limit of the frequency band for ensuring the measurement accuracy should be given according to Appendix B. A1 Overview
CB/T 16404--1996
Appendix A
(Appendix of the standard)
Calculation of sound field indication value
For each selected measurement base surface and measurement point array, the sound field indication value of each measured frequency band shall be calculated according to formulas (A1) to (A9). 42 Definition of sound field indication value
42.1 Indication value of sound field variation with time
Calculate the indication value of sound field variation with time at the corresponding measurement point on the measurement surface according to formula (A1): F
Where: I. - The average value of I calculated by formula (A2) for M short-time average sampling I. Note 9 M is generally taken as 10, and the short average time is recommended to be between 8: and 12:, or for periodic signals, any integer of the period. A2.2 Sound pressure-intensity indication value of the measuring surface is calculated by formula (A3): F,-L,-ual
-the sound pressure level of the measuring surface expressed in decibels, and its calculation formula is (A4): Where: L. —
L(dB)=10lg[
--The normal sound intensity level without a sign on the measuring surface expressed in decibels: Its calculation formula is (A3): Lun(dB)=10[
Wherein;
--The normal sound intensity without a sign at the measuring point
A2.3 Negative indication value of sound power filter
Negative indication value of sound power filter F is calculated according to formula (A6): F, =L,
Formula:
--The sound pressure level on the measuring surface expressed in decibels is calculated according to formula (44). (A1)
(A2)If the modified measurement point arrays according to step 2 do not meet the required accuracy, then measures shall be taken according to step B2. The modified measurement surface and measurement point array shall be used to measure the sound intensity level components and the corresponding sound pressure levels and recalculate the sound field indication values ​​F, F, and F. They shall be evaluated according to step B1 and measures shall be taken according to step B2. Repeat this process until the required accuracy is achieved. In the event that the repeated corrections do not meet the specified criteria, please record an invalid test result and explain the relevant reasons.
9 Calculation of sound power level
9.1 Calculate the local sound power of each facet element on the measurement surface. The local sound power W=Is
of each frequency band of each surface is calculated according to the following formula (11), where: W, is the local sound power of the surface element,
is the signed amplitude of the normal sound intensity component measured at the measuring point 1, and S, is the area of ​​the surface element.
When the normal sound intensity level Lm of the surface element is expressed as ××dB, the value of I is calculated according to the following formula: I =I.× 10w/15
When the normal sound intensity level La of the surface element i is expressed as (-)××dB, the value of 1 is calculated according to the following formula: I±-1.X10u/1g
where: 1, =10-13W/m
9.2 Calculation of noise source sound power level
The noise source sound power level of each frequency band is calculated according to formula (12): Lu(alB) = 10lg ZW,/W.
Where: W: local sound power of surface element i: W,——Chia sound power (=10-13W) #N—the total number of measurement points or surface elements.
***(12))
If
>W. of any frequency band is a negative value, the method of this standard is not applicable to this frequency band. When measuring according to this standard, the following contents should be collected and recorded. 10.1 Sound source to be measured
) Description of the sound source to be measured (including its size and surface characteristics). h) Characteristics of the sound source to be measured (variability, occurrence of periodicity, pure sound quality, etc.). c) Operating conditions.
d) Installation conditions.
10.2 Acoustic environment
a) Description of the test environment, including a sketch of the shell source position , shape and location of nearby objects, local topography and/or ground characteristics).
h) Description of the noise characteristics of the non-test sound source, including variability, occurrence of periods, and pure tone quality. c) Air temperature and static pressure.
d) Average wind speed and direction.
) Description of any equipment/methods used to minimize the effects of external noise. f) Qualitative description of any gas/air currents and instabilities. 10.3 Only
a) Equipment used for measurement, including name, model, serial number, manufacturer and probe configuration. b) Methods used for instrument calibration and field checks, including date of acquisition. c) Sound pressure residual intensity index for each band of the sound intensity measurement system when using different probe configurations. d) Date and location of calibration of the sound intensity measurement equipment. 10.4 Measurement Procedure
a) Description of each step of the measurement procedure.
b) Description of the probe fixing or support system during measurement. ) Quantitative description of the measurement surface and elements; a sketch should be provided. d) Description of the measurement array, giving the number and coordinates of each measuring point. c) Average time for each measuring point.
10.5 Scientific data
a) Table of sound field indication values ​​calculated for each set of measurements on each measuring surface of the saw. h) Graph or chart of calculated sound power levels in all frequency bands. Where an A-weighted sound power level is to be determined, the components of the bands that do not meet criteria 1 and/or 2 of Appendix B shall be omitted with an explanation of the effect of the omission, unless these components are negligible according to 4.3.
c) Explanation of the uncertainty of the sound power level in each frequency band measured by formula (B.3) that does not meet criterion 2 of Appendix B.
6.2.2 Description of the results of the field test in the reverse direction of the probe. e) Date of measurement (year/month/day)
6 Accuracy level of sound power level determination
The accuracy level of the final test shall be stated in accordance with Table 2. In special cases, when a certain test accuracy level can only be achieved within a limited frequency band, the 95% confidence limit of the frequency band for ensuring the measurement accuracy should be given according to Appendix B. A1 Overview
CB/T 16404--1996
Appendix A
(Appendix of the standard)
Calculation of sound field indication value
For each selected measurement base surface and measurement point array, the sound field indication value of each measured frequency band shall be calculated according to formulas (A1) to (A9). 42 Definition of sound field indication value
42.1 Indication value of sound field variation with time
Calculate the indication value of sound field variation with time at the corresponding measurement point on the measurement surface according to formula (A1): F
Where: I. - The average value of I calculated by formula (A2) for M short-time average sampling I. Note 9 M is generally taken as 10, and the short average time is recommended to be between 8: and 12:, or for periodic signals, any integer of the period. A2.2 Sound pressure-intensity indication value of the measuring surface is calculated by formula (A3): F,-L,-ual
-the sound pressure level of the measuring surface expressed in decibels, and its calculation formula is (A4): Where: L. —
L(dB)=10lg[
--The normal sound intensity level without a sign on the measuring surface expressed in decibels: Its calculation formula is (A3): Lun(dB)=10[
Wherein;
--The normal sound intensity without a sign at the measuring point
A2.3 Negative indication value of sound power filter
Negative indication value of sound power filter F is calculated according to formula (A6): F, =L,
Formula:
--The sound pressure level on the measuring surface expressed in decibels is calculated according to formula (44). (A1)
(A2)If the modified measurement point arrays according to step 2 do not meet the required accuracy, then measures shall be taken according to step B2. The modified measurement surface and measurement point array shall be used to measure the sound intensity level components and the corresponding sound pressure levels and recalculate the sound field indication values ​​F, F, and F. They shall be evaluated according to step B1 and measures shall be taken according to step B2. Repeat this process until the required accuracy is achieved. In the event that the repeated corrections do not meet the specified criteria, please record an invalid test result and explain the relevant reasons.
9 Calculation of sound power level
9.1 Calculate the local sound power of each facet element on the measurement surface. The local sound power W=Is
of each frequency band of each surface is calculated according to the following formula (11), where: W, is the local sound power of the surface element,
is the signed amplitude of the normal sound intensity component measured at the measuring point 1, and S, is the area of ​​the surface element.
When the normal sound intensity level Lm of the surface element is expressed as ××dB, the value of I is calculated according to the following formula: I =I.× 10w/15
When the normal sound intensity level La of the surface element i is expressed as (-)××dB, the value of 1 is calculated according to the following formula: I±-1.X10u/1g
where: 1, =10-13W/m
9.2 Calculation of noise source sound power level
The noise source sound power level of each frequency band is calculated according to formula (12): Lu(alB) = 10lg ZW,/W.
Where: W: local sound power of surface element i: W,——Chia sound power (=10-13W) #N—the total number of measurement points or surface elements.
***(12))
If
>W. of any frequency band is a negative value, the method of this standard is not applicable to this frequency band. When measuring according to this standard, the following contents should be collected and recorded. 10.1 Sound source to be measured
) Description of the sound source to be measured (including its size and surface characteristics). h) Characteristics of the sound source to be measured (variability, occurrence of periodicity, pure sound quality, etc.). c) Operating conditions.
d) Installation conditions.
10.2 Acoustic environment
a) Description of the test environment, including a sketch of the shell source position , shape and location of nearby objects, local topography and/or ground characteristics).
h) Description of the noise characteristics of the non-test sound source, including variability, occurrence of periods, and pure tone quality. c) Air temperature and static pressure.
d) Average wind speed and direction.
) Description of any equipment/methods used to minimize the effects of external noise. f) Qualitative description of any gas/air currents and instabilities. 10.3 Only
a) Equipment used for measurement, including name, model, serial number, manufacturer and probe configuration. b) Methods used for instrument calibration and field checks, including date of acquisition. c) Sound pressure residual intensity index for each band of the sound intensity measurement system when using different probe configurations. d) Date and location of calibration of the sound intensity measurement equipment. 10.4 Measurement Procedure
a) Description of each step of the measurement procedure.
b) Description of the probe fixing or support system during measurement. ) Quantitative description of the measurement surface and elements; a sketch should be provided. d) Description of the measurement array, giving the number and coordinates of each measuring point. c) Average time for each measuring point.
10.5 Scientific data
a) Table of sound field indication values ​​calculated for each set of measurements on each measuring surface of the saw. h) Graph or chart of calculated sound power levels in all frequency bands. Where an A-weighted sound power level is to be determined, the components of the bands that do not meet criteria 1 and/or 2 of Appendix B shall be omitted with an explanation of the effect of the omission, unless these components are negligible according to 4.3.
c) Explanation of the uncertainty of the sound power level in each frequency band measured by formula (B.3) that does not meet criterion 2 of Appendix B.
6.2.2 Description of the results of the field test in the reverse direction of the probe. e) Date of measurement (year/month/day)
6 Accuracy level of sound power level determination
The accuracy level of the final test shall be stated in accordance with Table 2. In special cases, when a certain test accuracy level can only be achieved within a limited frequency band, the 95% confidence limit of the frequency band for ensuring the measurement accuracy should be given according to Appendix B. A1 Overview
CB/T 16404--1996
Appendix A
(Appendix of the standard)
Calculation of sound field indication value
For each selected measurement base surface and measurement point array, the sound field indication value of each measured frequency band shall be calculated according to formulas (A1) to (A9). 42 Definition of sound field indication value
42.1 Indication value of sound field variation with time
Calculate the indication value of sound field variation with time at the corresponding measurement point on the measurement surface according to formula (A1): F
Where: I. - The average value of I calculated by formula (A2) for M short-time average sampling I. Note 9 M is generally taken as 10, and the short average time is recommended to be between 8: and 12:, or for periodic signals, any integer of the period. A2.2 Sound pressure-intensity indication value of the measuring surface is calculated by formula (A3): F,-L,-ual
-the sound pressure level of the measuring surface expressed in decibels, and its calculation formula is (A4): Where: L. —
L(dB)=10lg[
--The normal sound intensity level without a sign on the measuring surface expressed in decibels: Its calculation formula is (A3): Lun(dB)=10[
Wherein;
--The normal sound intensity without a sign at the measuring point
A2.3 Negative indication value of sound power filter
Negative indication value of sound power filter F is calculated according to formula (A6): F, =L,
Formula:
--The sound pressure level on the measuring surface expressed in decibels is calculated according to formula (44). (A1)
(A2)3
a) Equipment used for the measurements, including name, model, serial number, manufacturer and probe configuration. b) Methods used for instrument calibration and field checks, including date of acquisition. c) Sound pressure residual intensity index for each band of the sound intensity measurement system when different probe configurations are used. d) Date and location of calibration of the sound intensity measurement equipment. 10.4 Measurement procedure
a) Description of each step of the measurement procedure.
b) Description of the probe fixing or support system during the measurements. d) Quantitative description of the measurement surface and elements; a sketch should be provided. d) Description of the measurement array, giving the number and coordinates of each measurement point. c) Average time for each measurement point.
10.5 Scientific data
a) Table of calculated sound field indication values ​​to F for each set of measurements on each measurement surface. h) Graph or chart of calculated sound power levels for all frequency bands. Where an A-weighted sound power level is to be determined, the components of the bands that do not meet criterion 1 and/or criterion 2 of Appendix B shall be omitted but the effect of the omission shall be explained, unless these components can be ignored according to 4.3.
c) Explanation of the uncertainty of the sound power level in each frequency band measured by formula (B.3) that does not meet criterion 2 of Appendix B. 6.2.2 Description of the results of the field test in the reverse direction of the probe e) Date of measurement (year/month/day)
6 Accuracy level of sound power level determination
The accuracy level of the final test shall be explained according to Table 2. In special cases, when a certain test accuracy level can only be achieved within a limited frequency band, the 95% confidence limit of the frequency band to ensure the measurement accuracy shall be given according to Appendix B. A1 Overview
CB/T 16404--1996
Appendix A
(Appendix of Standard)
Calculation of sound field indication value
For each selected measurement base surface and measurement point array, the sound field indication value of each measured frequency band is calculated according to formulas (A1) to (A9). 42 Definition of sound field indication value
42.1 Indication value of sound field changing with time
Calculate the indication value of sound field time changing at the corresponding measurement point on the measurement surface according to formula (A1): F
Where: I. - The average value of I. obtained by calculating M short-time average sampling I. according to formula (A2): Note 9 M is generally taken as 10, and the short average time is recommended to be between 8: and 12:, or for periodic signals, any integer of the period. A2.2 The sound pressure and sound intensity indication value of the measuring surface are calculated according to formula (A3): F, —L, —ual
- the sound pressure level of the measuring surface expressed in decibels, and its calculation formula is (A4): where: L. —
L(dB)=10lg[
--The normal sound intensity level without a sign on the measuring surface expressed in decibels: Its calculation formula is (A3): Lun(dB)=10[
Wherein;
--The normal sound intensity without a sign at the measuring point
A2.3 Negative indication value of sound power filter
Negative indication value of sound power filter F is calculated according to formula (A6): F, =L,
Formula:
--The sound pressure level on the measuring surface expressed in decibels is calculated according to formula (44). (A1)
(A2)3
a) Equipment used for the measurements, including name, model, serial number, manufacturer and probe configuration. b) Methods used for instrument calibration and field checks, including date of acquisition. c) Sound pressure residual intensity index for each band of the sound intensity measurement system when different probe configurations are used. d) Date and location of calibration of the sound intensity measurement equipment. 10.4 Measurement procedure
a) Description of each step of the measurement procedure.
b) Description of the probe fixing or support system during the measurements. d) Quantitative description of the measurement surface and elements; a sketch should be provided. d) Description of the measurement array, giving the number and coordinates of each measurement point. c) Average time for each measurement point.
10.5 Scientific data
a) Table of calculated sound field indication values ​​to F for each set of measurements on each measurement surface. h) Graph or chart of calculated sound power levels for all frequency bands. Where an A-weighted sound power level is to be determined, the components of the bands that do not meet criterion 1 and/or criterion 2 of Appendix B shall be omitted but the effect of the omission shall be explained, unless these components can be ignored according to 4.3.
c) Explanation of the uncertainty of the sound power level in each frequency band measured by formula (B.3) that does not meet criterion 2 of Appendix B. 6.2.2 Description of the results of the field test in the reverse direction of the probe e) Date of measurement (year/month/day)
6 Accuracy level of sound power level determination
The accuracy level of the final test shall be explained according to Table 2. In special cases, when a certain test accuracy level can only be achieved within a limited frequency band, the 95% confidence limit of the frequency band to ensure the measurement accuracy shall be given according to Appendix B. A1 Overview
CB/T 16404--1996
Appendix A
(Appendix of Standard)
Calculation of sound field indication value
For each selected measurement base surface and measurement point array, the sound field indication value of each measured frequency band is calculated according to formulas (A1) to (A9). 42 Definition of sound field indication value
42.1 Indication value of sound field changing with time
Calculate the indication value of sound field time changing at the corresponding measurement point on the measurement surface according to formula (A1): F
Where: I. - The average value of I. obtained by calculating M short-time average sampling I. according to formula (A2): Note 9 M is generally taken as 10, and the short average time is recommended to be between 8: and 12:, or for periodic signals, any integer of the period. A2.2 The sound pressure and sound intensity indication value of the measuring surface are calculated according to formula (A3): F, —L, —ual
- the sound pressure level of the measuring surface expressed in decibels, and its calculation formula is (A4): where: L. —
L(dB)=10lg[
--The normal sound intensity level without a sign on the measuring surface expressed in decibels: Its calculation formula is (A3): Lun(dB)=10[
Wherein;
--The normal sound intensity without a sign at the measuring point
A2.3 Negative indication value of sound power filter
Negative indication value of sound power filter F is calculated according to formula (A6): F, =L,
Formula:
--The sound pressure level on the measuring surface expressed in decibels is calculated according to formula (44). (A1)
(A2)
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