The purpose of this standard is to provide a test procedure and guidelines for acoustic conduction testing to determine whether a sample can withstand the vibration caused by a specified noise environment or the tendency to be formed by it. GB/T 2423.47-1997 Environmental testing for electric and electronic products Part 2: Test method Test Fg: Acoustic vibration GB/T2423.47-1997 Standard download decompression password: www.bzxz.net

GB/T2423.47-1997
This standard is equivalent to the International Electrotechnical Commission standard IEC68-2-65 "Environmental testing Part 2: Test methods Test Fg: Sound and vibration 1993 1st edition.
Appendix A and Appendix B of this standard are both informative appendices. This standard is proposed by the Ministry of Electronics Industry of the People's Republic of China. This standard is under the jurisdiction of the National Technical Committee for Environmental Technical Standardization of Electrical and Electronic Products. The drafting units of this standard are the Fifth Research Institute of the Ministry of Electronics Industry and the Standardization Research Institute of the Ministry of Electronics Industry. The main drafters of this standard are Ji Chunyang, Li Xianshan, Wang Talan, Jie He, and Zhou Xincai. GB/T2423.47—1997
IEC Foreword
1) IEC (International Electrotechnical Commission) is a worldwide standardization organization composed of all national electrotechnical technical committees (IEC national subcommittees). The purpose of IEC is to promote international cooperation on relevant standards and all issues in the fields of electrical and electronic engineering. To this end, the IEC publishes international standards in addition to other activities. Standards are formulated by its technical committees, and any national TEC subcommittee interested in a standard topic can participate in the formulation of the standard. International governmental and non-governmental organizations that have a cooperative relationship with the IEC also participate in the formulation of standards. The IEC works closely with the International Organization for Standardization (ISC) through an agreement between the two organizations. 2) Formal resolutions or agreements on technical issues formulated by the technical committees of the International Electrotechnical Commission, in which all national committees with special concerns about the issue participate, which reflect and express the international consensus on the issue as much as possible. 3) These resolutions or agreements are accepted by the national committees in the form of recommended standards for international use. 4) In order to promote international unification, the International Electrotechnical Commission hopes that all member countries will adopt the contents of the recommended standards of the International Electrotechnical Commission as their national standards when formulating national standards, as long as the specific conditions of the country permit. Any differences between the recommended standards of the International Electrotechnical Commission and the national standards should be clearly pointed out in the national standards as much as possible. This standard was prepared by the International Electrotechnical Commission Technical Committee 50 (Environmental Testing) Subcommittee 50A (Vibration, Shock and Other Mechanical Testing).
This standard text is based on the following documents: DIS
50A(CO)226
Voting Report
$0A(CO)228
All information on the voting for this standard is listed in the voting report in the table above. Annexes A and B are both informative appendices. 1 Purpose
National Standard of the People's Republic of China
Environmental testing for eleclric and electronic products
Part 2: Test methods
Test Fg: Vibrationl , acoustically inducedCB/T 2423. 47-1997
idt IEC 68-2-65:1993
The purpose of this standard is to provide a test procedure and guidelines for determining whether a sample can withstand the vibration caused by a specified noise environment or the tendency to form a market test. No requirements are made for acoustic tests in sound pressure level environments below 120dB. Under the specified acoustic test conditions, determine the mechanical weaknesses and performance degradation of the test sample and evaluate their acceptability in conjunction with other provisions. In some cases, this test method is also used as a method to determine the mechanical strength or fatigue resistance of the test sample. This standard describes the process of acoustic vibration testing and measuring the sound pressure level in a noisy environment and takes into account the need to measure the vibration response of the test sample at a specific point. It also provides guidance for selecting the noise environment, spectrum, sound pressure level and exposure duration. 2 Reference standards
The following standards contain provisions that 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. GB/T2298--91 Mechanical vibration and impact terminology (nenISO2041:1990) GB2421-89 Basic environmental test procedures for electronic products (cgVIEC68-11988) IEC50(151)1978 International Electrotechnical Vocabulary (IEV) - Chapter 151: Electromagnetic equipment IEC50(801):1984 International Electrotechnical Vocabulary (IEV) IEC651:1979 Sound level meter
ISO266:1975 Common frequencies in acoustic measurement Chapter 801: Acoustics and electroacoustics
ISO2671:1982 Environmental testing of aircraft equipment - Part 3.4: Urban vibration 3 Definitions, symbols and abbreviations
This standard refers to the following definitions. The terms used generally adopt the terms specified in GB/T2298, GB2421 and IEC50(801). For the convenience of the reader, the definitions in these standards are listed here and the differences are indicated. Deviations from these standards are also listed (see 3.2). The following additional terms and definitions apply to this standard. 3.1 Definitions
3.1.1 Acoustic horn (not equivalent to IEC 50 (801) 07-12) A horn with a cross-section that usually varies exponentially, used to connect the sound source to the test chamber, such as the inside of a reverberation chamber, so that the impedance between the sound source and the test chamber is matched to maximize energy transfer. NOTE: Each acoustic horn has its own transfer characteristics. These characteristics affect the sound harmonics. Approved by the State Administration of Technical Supervision on September 1, 1997 and implemented on October 1, 1998
GB/T 2423. 47---1997
3.1.2 Analysis integration time analysis integration time The duration of the signal to be averaged (see A8). 3.1.3 Bandwidth (equivalent to A31 in GB/T2298-91) The difference between the rated upper and lower cut-off frequencies. Note:
1 The unit is Hz.
2 The percentage of the passband to the center frequency.
3 The difference between the upper and lower cut-off frequencies, measured in terms of frequency. 3.1.4 Overall sound-pressure level (OASPL) The sound pressure value calculated from the sound pressure level of 1/3 octave or 1 octave. Lc= 10log1Z10z,10
Where: L total sound pressure level, dB:
L,——the sound pressure level on the first 1/3 octave or 1 octave: m--the number of 1/3 octave or 1 octave 3. 1. 5 Center frequency center frcqucncy (equivalent to A42 of GB/T 2298-91) The geometric mean of the nominal cutoff frequency of the passband, Note
1GB/T2258 defines the upper and lower cutoff frequencies of the passband as the frequency outside the maximum response frequency of the double filter, at which the response to the sinusoidal signal is 3B lower than the maximum response.
2 Its geometric mean is equal to (fxf.)\,fi and f; are the cutoff frequencies. 3.1.6 Constant-handwidth filter (equivalent to A33 of GR/T2298-91) A filter with a fixed value that is independent of the center frequency when the frequency is in Hz. 3.1.7 Cut-off frequency (of acoustic hurn) The frequency below which the main characteristic wave characteristics of the acoustic hurn become ineffective. 3.1.8 Diffuse sound field (equivalent to 03-31 of IEC 50 (801)) A sound field with statistically uniform energy density that is randomly distributed in all propagation directions in a given area. In a diffuse sound field, the sound pressure level measured by a directional sound transmitter is the same in any direction. 3.1.9 Electro-or hydraulic airflow loudspeaker Electro-or hydraulic airflow loudspeaker is a common noise source in the laboratory. Its function is to simulate the sound pressure level changes in a high noise environment. It is a wide-band sound transducer powered by pressurized gas and modulated by a solenoid valve or a hydraulic valve. Note: The speaker provides a continuous energy spectrum with random amplitude distribution over a wide frequency band and has the ability to form specified acoustic harmonics in acoustic tests (see A5). 3.1.0 frequency interval (equivalent to 7-01 of IEC 50 (801)) The ratio of two frequencies.
3.1.10.1 octave
The interval between two frequencies whose ratio is 2. 3.1.10.2 1/3 octaveome-third octave (1/3)The interval between two frequencies whose ratio is 2 raised to the power of 1/3. 3.1.10.3 1/12 octaveone-twelfth octave (1/12)The interval between two frequencies whose ratio is 2 raised to the power of 1/12. 3.1.11 measuring points are specific points at which data are collected during the test. There are two types of measuring points. Note: In order to estimate its working state, it is necessary to set measuring points on the sample. However, in this standard, measuring points in this sense are not considered. 3.1.11.1 Check-pointsCB/T 2423.47—1997
Fixed points on an imaginary surface surrounding the sample and at a fixed distance from the sample. 3.1.11.2 Reference points are points selected from the check-points, whose reference points are used to control the test and meet the requirements of this standard. 3.1.12 Multipoint control, multipoint cnnirut Control completed by the signal average value at the reference point (see 3.1.11.2) Note: When using multipoint control, each microphone signal corresponds to the sound pressure level of a part. The average sound level 1xv can be defined according to [1-36] of IEC:50 (801>, with
where: n——number of reference points;
110520
Lay=lolangle
the sound pressure level of the first 1/3 or 1 octave. L
Or, when the difference between the sound levels is small, the average sound pressure level can be taken as the arithmetic mean. For example, when the difference in sound pressure level is 6B, the error of taking the arithmetic mean is approximately 0.5B.
3.1.13 Narrowband filter narrowbandfrequencylilter passband is a bandpass filter with a relatively large passband (usually less than 1/3 times the range). 3.1.14 Broadband filter: Broadband frequency or wide band filter: A bandpass filter with a relatively wide passband (usually greater than 1 octave). 3.1.15 Progressive wave tube: A tube in which sound waves are propagated from a sound source along the tube. The acoustic horn is connected to the sound source and the test section through the traveling wave tube. Note: A sound absorption terminal device is configured at the test end to minimize the reflection of sound waves propagating within the frequency range used (see A2). 3.1.16 Proportional-bandwidth filter (equivalent to A34 of GB/T2298-91): A filter whose bandwidth is proportional to the center frequency. Note: 1 octave bandwidth and 1/3 octave bandwidth are typical proportional bandwidth filters. 3.1.17 Reverberation room: Reverberation room (not equivalent to FC, 11-13 of 1EC50 (801)) The surface has high hardness and high reflectivity, and makes the sound field in it a highly reverberant room. 3.1.18 Sound absorption coefficient soundahsorptioncocfficient (not equivalent to 11-02 of 1EC50 (801)) The ratio of the sound power absorbed by the material surface without being reflected and the sound power emitted by the human body under given frequency and specified conditions. Note: Sound absorption has the characteristic of converting the sound energy of materials and objects into heat energy. 3.1.19 Sound pressure ep (equivalent to 01-20 of IFC50 (801) except as noted below) Unless otherwise specified, sound pressure is defined as the root mean square value of the instantaneous sound pressure within a given time interval. Method: The static pressure generated by the sound wave will cause a change in pressure when disturbed by the gas medium, and its sound pressure characteristics will also change. 3.1.19.1 Sound pressure level L, gned-pressure level L, (equivalent to 02-07 of IFC50 (801)) top—20logto
EaB))
3.1.20 Standing wave tube This type of reference sound [Ep, = 20μPa (see 3.2) produces a periodic sound wave with a fixed spatial distribution, which is composed of the addition of traveling waves and reflected waves of corresponding frequencies. Note: The key to a standing sound wave is the presence of a complete or partially solid pressure node in space and the presence of a reflected wave. The acoustic horn matches the source and the stationary tube and terminates on a rigid axial base cheek adjustable reflector. The special wave tube provides an effective method for generating discrete frequencies of sound pressure level (see A4). 3.2 Symbols and abbreviations The following symbols and abbreviations are used, and the abbreviations and definitions are given in cross-reference. 04SP1: Total sound pressure level (see 02-07 of IEC50 (801> + see 3.1.4). LG: Total sound pressure level, in dB (see 3.1.1) L: Sound pressure level in the first 1/3 or 1 octave band (see 3.1.4) L.; Sound pressure level (see 3.1.19.1)
Lav: Average sound pressure level (see 3.1.12)
GB/T 2423. 47-- 1997
p; root mean square value of sound pressure, in Pa or N/m (see 3.1.19) Po: international benchmark sound pressure value, defined as 2X10-5Pa or 20μPa (according to IEC651, in air medium), 1μPa in other media.
4 Test sound environment and test requirements
4.1 Test sound environment
In order to determine the working and tolerance of electrical and electronic products in the specified high-intensity noise field, it is necessary to carry out acoustic vibration tests. The fluctuating pressure environment may be a complex combination of traveling waves and reverberation sound fields. This acoustic test environment can produce very high local sound pressure levels due to resonance in the cavity where noise is applied. This acoustic test environment can be obtained from actual measured data on site or in flight tests or from general levels specified for specific locations of the product, as shown in Figures 1, 2 and 3. The applied test spectrum may contain frequency components higher or lower than those given in the figure.
Note: For sound pressure levels related to the flight environment, see ISO2671. 4.1.1 Reverberation field test
The reverberation field is usually used for test samples intended to be placed in a closed space when the pressure fluctuations are uniformly distributed for the test sample. However, it can also be used to test Self-enclosed test specimens, such as the drogue hoods of large vehicles, cannot be simulated any other way. Reverberation can be generated in enclosures by the excitation of boundary structures and noise radiation from engines caused by disturbances in the flow or by fluid separation on the surface, as well as in enclosed spaces such as the pressure vessel of a gas-cooled reactor (see A1). 4.1.2 Traveling wave tests are used to simulate areas where sound energy strikes the surface of the test specimen. Examples of such environments are external assemblies on aircraft that are excited by aerodynamic turbulence, heat shields for rocket engines, aircraft and house wings close to jets, propellers, etc. slurry, etc. (see A2). 4.1.3 Cavity resonance test
It is used to simulate the internal sound field of a cavity that is in acoustic excitation or resonates due to the turbulence in the cavity, producing very high sound pressure levels. For example, the landing gear cavity and combustion chamber when the wheels are lowered for landing (see A3). 4.1.4 Standing wave test
The standing wave tube test can produce very high pure sound pressure levels and is used to evaluate and develop components that may be exposed to extremely high sound pressure levels in the case frequency band (see A4).
4.2 Sound source
Guidelines on how to select a suitable sound source according to the test requirements are given in Chapter A5 of Appendix A. 4.3 Measuring equipment
In order to monitor the sound pressure level of the sound field around the test sample, it is necessary to measure the vibrations caused by the sound on the test sample and analyze the frequency components of these measurements (see 4.3.3).
4.3.1 Acoustic Measurement
The monitoring measurement system shall be able to measure the sound pressure level in the frequency range of 22.4Hz~11200Hz in either 1 octave or 1/3 octave, with the center frequency between 31.5 Hz/25 Hz (1 or 1/3 octave) and 8 kHz/10 kHz. The measurement system shall have a flat frequency response within the frequency range of interest, and its tolerance is shown in Table 1. Table 1 Tolerance of Acoustic Measurement
Frequency Range
126~2500
2501～1200
The microphone used shall be capable of random incidence measurement and have the ability to measure more than times the rated RMS peak value. GB/T 2423.47—1997
The monitoring and measuring system shall be capable of measuring the total sound pressure level of the specified test and the sound pressure level of each white band by 10 lB. 4.3.2 Vibration response measurement
The vibration response measurement of the test sample can be based on acceleration and/or strain measurement (if necessary, displacement or velocity response can also be monitored). The monitoring equipment used for vibration response measurement should have the ability to measure the total vibration response in the frequency range of not less than 16Hz~2000Hz. When measuring the frequency range of interest, the equipment should have a flat frequency response characteristic and be compatible with the purpose and measurement type. 4.3.3 Analysis of results
The measurement data should be obtained from 4.3.1. If necessary, 4.3.2 can also perform frequency component analysis. a) Sound measurement should have an analysis capability of at least 1 octave, preferably 1/3 octave. b) The vibration response measurement equipment usually needs to have a higher resolution analysis capability. The analysis range uses a proportional bandwidth filter such as 1/12 octave, or an equal bandwidth filter of 10Hz. The specific analysis bandwidth to be used shall be determined according to the relevant specifications. 4.4 Test requirements
4.4.1 Equipment type
The test equipment shall be selected according to the time and space characteristics of the sound field when simulating the scene or working. At present, the main equipment used to provide the test sound field is the reverberation chamber or test box. The following test requirements refer to this test condition. Other types of equipment are described in Appendix A. The requirements for equipment types are specified by the relevant specifications.
If the test sample is exposed to a high-intensity sound environment and some other environmental parameters at the same time, such as extreme temperature, the sound test must comply with the requirements of this standard for comprehensive testing.
4.4.2 Installation
The test sample shall be installed in the middle of the reverberation chamber. Its working surface shall not be parallel to the wall (including the top and the ground) as much as possible. The sample shall be elastically suspended or supported in the reverberation chamber. The relevant specifications shall specify the preferred installation form or connection point when necessary. The natural frequency of the sample in the suspension or support system shall be lower than 25Hz or one-fourth of the lowest test frequency, whichever is lower. The distance between the test point and the sample surface must be greater than 1/2 wavelength of the lowest frequency or greater than half the distance between the sample and the wall, whichever is less. If this is not possible, a sensor must be placed at a distance less than 1/2 wavelength. The noise thus measured is greatly modified by reflections from the sample and this must be taken into account when evaluating the test results. If structural components are required, care must be taken to prevent variations in the noise field or the introduction of external vibrations, either between the sample and the elastic suspension or on the elastic suspension itself. The placement of any connections to the sample, such as cables, conduits, etc., should simulate the constraints and mass of the sample in its operating position by fastening the cables, conduits, etc. to the mounting fixture. 4.4.3 Sample Tester
Whenever possible, the relevant specification should specify the number, type and location of sensors (velocimeters, microphones, strain gauges, etc.) to be installed on the test sample.
The calibration of each sensor should be valid.
4.4.4 Pre-adjustment of reverberation space
4.4.4.1 Number and position of test points
There shall be at least three microphones for controlling the sound pressure level of the wall in the surround test sample. According to the relevant specifications, the number and installation position of the microphones shall be on three orthogonal axes of the sample surface (see Figure 5). If the spectrum is pre-adjusted by simulation parts, the position of the microphones shall be consistent with the position in the subsequent test. 4.4.4.2 Control of spectrum
The response of the microphone at each test point shall be analyzed by 1 or 1/3 octave band according to the relevant specifications. The average sound pressure level in each bandwidth can be obtained according to 3.1.12. Then the average total sound level can be calculated from it. The sound pressure level in each bandwidth and the sound pressure level of the average spectrum shall be within the spectrum tolerance specified in Figures 1, 2 and 3 or within the tolerance of other spectra specified in the relevant specifications. The average total sound level must be within the tolerance range specified in the test. The integration time specified in the relevant specifications should be long enough to ensure the statistical confidence of the results. The pre-adjustment time should be long enough to enable real-time analysis of the response of the microphone at the test point to ensure that the sound pressure level during the pre-adjustment test is within the specified tolerance.
CB/T2423.47—1997
1 The relevant specifications should specify the maximum allowable deviation of the sound pressure level and the total sound pressure level of each microphone in each forehead band. 2 If the relevant specifications require 1/3 octave analysis, a 1/3 octave spectrum needs to be provided. 4.4.4.3 Spectral shaping
To avoid the test sample being damaged by over-testing during the sound field pre-adjustment, the sound field should be pre-adjusted using a simulant instead of the test sample. When the volume of the test sample is much smaller than the volume of the reverberation chamber, an empty reverberation chamber can be used to establish the sound field. 5 Severity level
The sound field severity level consists of the total sound pressure level (OASPL), spectrum shape and exposure duration. The relevant specifications select the total sound pressure level and the minimum exposure duration from Table 2, and the spectrum is selected from Figures 1, 2, and 3. Their application guidelines are given in A6. Table 2 Total sound pressure level and exposure duration
Total sound pressure level
120±1
130±1
140±1
150±1
170±1
6 Pretreatment
Exposure duration
In order to make the test sample stable (thermal, mechanical, etc.), it should be pretreated under standard atmospheric conditions according to the requirements of relevant specifications. 7 Initial detection
The appearance, size and performance of the test sample should be inspected according to the provisions of relevant specifications. 8 Test
8.1 Routine test
Test samples using sensors according to relevant specifications should be installed according to the requirements of 4.4.2. According to the provisions of 4.4.4.1, the test points are set for testing. The spectrum shape is specified in 4.4.4.3. The control of the spectrum shape is specified in 4.4.4.2. The severity level is specified by the relevant specifications in accordance with the requirements of Chapter 5. Record the signals of the control microphone and the sensor on the test sample for later data analysis (see 4.4.4.2). 8.2 Accelerated test
Accelerated test is to expose the test sample to a working environment with a higher sound pressure level than normal in order to reduce the test time when the working life of the product is very long and conventional tests cannot be applied. There are no clear rules and test procedures for accelerated testing. The test method can be specified in the relevant specifications. Appendix A7 gives the common methods of accelerated testing. 9 Intermediate testing
When the relevant specifications require it, the test sample should be operated and functionally tested during the test. 10 Recovery
When the relevant specifications specify it, after the conditioning test and before the final test, it is sometimes necessary for a period of time to allow the test sample to reach the same state as that existing during the initial test, such as temperature. 11
Final test
GB/T 2423.47—1997
The test samples shall be tested for appearance, size and performance according to the relevant specifications. During the test, the signals from the control microphone and the sample test sensor (if any) must be processed to check whether the requirements of this standard and the relevant specifications are met.
The relevant specifications shall specify the criteria for acceptance or rejection of the test products. Provisions to be made in the relevant specifications
When the relevant specifications include this test, the following corrections should be given according to the application. Pay special attention to the clauses marked with "\" because these information are essential.
8) Bandwidth of the filter' (4.3.3);
b) Type of equipment* (4.4.1):
c) Installation (4.4.2);
d) Test sensor (4.4.3);
c) Location and number of detection points* (4.4.4.1); f) 1/3 or 1 octave group analysis (4.4.4.2): Text) No shape (4.4.4. 2 and Chapter 5);
h) analysis integration time* (4.4.4.2);1)) maximum allowable change in sound pressure level in the frontal band (4.4.4.2);j) 1/3 octave analysis spectrum (4.4.4.2);k) total sound pressure level (Chapter 5);
1) minimum exposure duration (Chapter 5):m) pretreatment (Chapter 6);
) initial test (Chapter 7)
0) accelerated test procedure, if required (8.2),p) intermediate test (Chapter 9):
g) recovery (Chapter 10);
) final test* (Chapter 11 Chapter)
s) Acceptance and rejection criteria (Chapter 11). PbzxZ.net
GB/T 2423. 47—1997
3dB/ocr
10dR/act
3dB/oct
·todB/oct
1/3 signal frequency center frequency,Hz
Figure 1 Acoustic test 1/3 octave spectrum
Axial flow fan
Centrifugal fan
2004000500c
Octave center frequency, H2
Figure 2 Octave spectrum of fan (see Appendix B E4]) 10-
GB/T 2423.47-1997
200040008000
Centre frequency of the wrong circuit, Hz
Figure 3T. Octave spectrum of industrial machinery noise (see -47 in Appendix B) Test sample
2Take the smaller value of //2 or D/2
Is the wavelength of the lowest frequency used
Smooth connection between horn and chamber
Figure 1 Passband installation position of microphone around test sample Test sample
GB/T 2423.47-1997
Imaginary surface
Figure 5 Normal installation position Mi of microphone detection points (1--6) on the imaginary surface around the test sample
The above is the length of the test sample
Figure 6 Normal installation position of microphone detection points around the long cylindrical test sample
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