This standard specifies the method for measuring the emission sound pressure level at the working position and other designated positions near machines and equipment in a semi-reverberant field. The emission sound pressure level is measured using A-weighting, and the C-weighted peak can be measured if necessary. GB/T 17248.3-1999 Acoustics Noise emitted by machines and equipment - Field simplified method for measuring the emission sound pressure level at the working position and other designated positions GB/T17248.3-1999 Standard download decompression password: www.bzxz.net
This standard specifies the method for measuring the emission sound pressure level at the working position and other designated positions near machines and equipment in a semi-reverberant field. The emission sound pressure level is measured using A-weighting, and the C-weighted peak can be measured if necessary.

GB/T17248.3—1999
This standard is equivalent to the international standard ISO11202:1995 "Simplified method for measuring the sound pressure level of noise emitted by acoustic machines and equipment at work and other designated positions on site". This standard is the third standard in the GB/T17248.1~17248.5 series of standards, which include: GB/T17248.1 Noise emitted by acoustic machines and equipment Guidelines for the use of basic standards for determining the sound pressure level of noise emitted at work and other designated positions
GB/T17248.2
Measurement of the sound pressure level of noise emitted by acoustic machines and equipment at work and other designated positions Engineering method approximately free field above a reflecting surface GB/T17248.3 Acoustics Noise emitted by machines and equipment. Field simplified method for measuring the emission sound pressure level at the working position and other designated positions
GB/T17248.4 Acoustics. Noise emitted by machines and equipment. The emission sound pressure level at the working position and other designated positions is determined by the sound power level
GB/T17248.5 Acoustics. Noise emitted by machines and equipment. Environmental correction method for measuring the emission sound pressure level at the working position and other designated positions
This series of standards specifies various methods for measuring the emission noise of machines and equipment or equipment parts. Appendix A of this standard is the appendix of the standard.
Appendix B, Appendix C and Appendix D of this standard are all indicative appendices. This standard is proposed and managed by the National Technical Committee for Acoustics Standardization. The drafting units of this standard are: the Seventh Research Institute of China State Shipbuilding Corporation and the Institute of Acoustics of the Chinese Academy of Sciences. The main drafters of this standard are: Lu Qiaoyun and Lv Yadong. 369
GB/T17248.31999
ISOForeword
The International Organization for Standardization (ISO) is a worldwide federation of national standardization committees (ISO member countries). The formulation of international standards is usually completed by ISO technical committees. Each member country has the right to participate in a technical committee when it is interested in a standard determined by a technical committee. Governmental and non-governmental international organizations associated with ISO may also participate in the work. The International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC) maintain close cooperation in all aspects of electrotechnical standardization. The draft international standards adopted by each technical committee shall be distributed to each member country for voting. The draft international standard requires at least 75% of the member countries to vote in favor before it can be published as an international standard. International Standard ISO11202:1995 was drafted by ISO/TC43 Acoustics Technical Committee SC1 Noise Subcommittee. Appendix A of this standard is the standard appendix, and Appendix B, Appendix C and Appendix D of this standard are indicative and for reference only. 370
GB/T17248.3—1999
This standard specifies a method for measuring the emission sound pressure level at the working position and other specified positions near the machine or equipment. The method specified in this standard is consistent with the method specified in GB/T17248.2 (engineering method) except for the following cases: a) on-site measurement is allowed,
b) a simplified method for determining the local environmental correction value is specified, and the result is close to the result obtained in the approximate free field above a reflecting surface. The correction can be used to obtain the emission sound pressure level at the specified position (including the working position), and the accuracy level of the result is simple level. This standard is a standard in the GB/T17248.1~17248.5 series of standards, which specifies various methods for determining the noise emission of machines and equipment or equipment parts. GB/T17248.1 provides guiding principles for how to choose the specific method for determining the emission sound pressure level of machines and equipment, and provides standard details of various methods for determining the sound power level. 371
National Standard of the People's Republic of China
Noise emitted by machinery and equipment
Simplified method for measuring emission sound pressure levels at work stations and at other specified positions--Survey method in situ1 Scope
1.1 Overviewwww.bzxz.net
GB/T 17248.3—1999
eqvISO11202:1995
This standard specifies the method for measuring emission sound pressure levels at work stations and at other specified positions near machinery and equipment in a semi-reverberant field. The emission sound pressure level is measured using A-weighting, and C-weighting peak value can be measured if necessary. Note 1: The contents of this standard and related standards are summarized in Table 1 of GB/T 17248.1. In order to minimize the influence of other sound reflections from reflective surfaces other than the plane where the machine equipment is placed, a method for determining the local environment correction value is given. The correction value is based on the sound absorption (equivalent sound absorption area) of the test room. The working position can be located in the indoor open space where the sound source is working, or in the operating room fixedly connected to the sound source, or in a closed space away from the sound source. There can be one or more designated positions near the machine that is attended or unattended, which can be used as bystander positions. This standard specifies the requirements for the test environment and instrument accuracy (simple level). Specific instructions are given for the installation and operation of the machine under test, as well as the selection of the microphone placement position at the working position and other designated positions. The purpose of the measurement is to compare the performance of a given series and different machine equipment units under specified environmental conditions and uniform installation and operation conditions. The data obtained can also be used for the marking and verification of emission sound pressure level noise labels as specified in GB/T14574. Note 2: At any given location and given installation and operating conditions related to a specific machine, the emission sound pressure level determined according to this standard method is generally lower than the sound pressure level obtained by directly measuring the sample machine in a typical workplace, due to the influence of reverberation and other machines. For the calculation method of the sound pressure level near a single machine running in a workplace, refer to ISO/TR11690-3. Generally, the difference between the two is 1 to 5 dB, and the difference is greater in some cases.
1.2 Noise and noise source types
The method specified in this standard is applicable to all types of machines, including mobile and fixed, indoor or outdoor machines. This method is applicable to machines of all sizes and all types of noise defined in GB/T14259 and ISO12001. 1.3 Test environment
This measurement method is applicable to indoor or outdoor environments that meet the specified requirements with one or more reflecting planes. 1.4 Specified locations
This standard applies to work positions and other specified locations where the emission sound pressure level is to be measured. Some examples of locations where measurements can be made are: a) a work position near the machine being measured, as is the case with many industrial machines and household appliances; b) a work position in an operating room that is an integral part of the machine being measured. c) a working position in a partially or fully enclosed space (or behind a barrier) which is an integral part of the machine equipment provided by the manufacturer; d) a working position in which the machine being tested is partially or fully enclosed, which is the case with some large industrial machines; e) a position of a bystander who is not responsible for operating the machine; f) other specified positions, not necessarily working positions or bystander positions; the working position may also be located along a specified path of movement of the operator 1.5 Measurement uncertainty It is not possible to give a widely applicable value for the standard deviation of the reproducibility of the emission sound pressure level at the working position. Guidance is given in Chapter 4 of this standard.
2 Cited standards
The clauses contained in the following standards constitute the clauses of this standard through reference in this standard. When this standard is published, the versions shown are 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/T3102.7—1993 Acoustic quantities and units (eqvISO31:1992) GB/T3222—1994 Acoustic environmental noise measurement method (neqISO1996-1:1982) GB/T3767-1996 Acoustic sound pressure method for determining the sound power level of noise sources Engineering method for approximate free field above reflecting surface (eqvISO 3744:1994)
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 (eqv ISO 3746:1995)
GB/T 3785—-1983
3 Electrical and acoustic properties and test methods of sound level meters Acoustics Terminology
GB/T 3947-1996
GB/T 14259--1993
Acoustics Standard guide for the measurement of airborne noise and the evaluation of its impact on people (neg ISO2204:1979)
Acoustics Noise labels for machines and equipment (negISO4871:1984) GB/T.14574--1993
GB/T 15173—1994
Sound calibrator (eqvIEC1014:1989) GB/T17181—1997 Integrating average sound level meter (idtIEC804:1985) GB/T17248.11) Acoustics Noise emitted by machines and equipment Determination of emission sound pressure levels at work and other specified locations Guide to the use of basic standards (eqvISO11200:1995) GB/T 17248.2—1999
Acoustics Noise emitted by machines and equipment Measurement of emission sound pressure levels at work and other specified locations Engineering method for approximation to free field above a reflecting surface (egvISO11201:1995) GB/T17248.4—1998
Acoustics Noise emitted by machines and equipment Determination of emission sound pressure levels at work and other specified locations from sound power levels (eqvISO11203:1995) GB/T 17248. 5--1999
Acoustics Noise emitted by machines and equipment - Measurement of emission sound pressure levels at work and other specified locations - Method with environmental correction (eqvISO11204:1995) ISO 4871:1996 Acoustics —
- Nominalization and verification of noise emission values ​​from machines and equipment ISO7779:1988 Acoustics
Measurement of airborne sound emitted by computers and business equipment ISO/TR11690-3:1997 Acoustics — Recommended practices for the design of low-noise workplaces containing machines - Part 3: Sound propagation and noise prediction in workplaces ISO 12001:1996 June
1) This standard is to be published soon.
Noise emitted by machines and equipment
-Drafting of noise test procedures and the criteria proposed 373
3 Definitions
GB/T17248.3-1999
This standard adopts the following definitions. Other acoustic terms, quantities and units shall be in accordance with the provisions of GB/T3947 and GB/T3102.7. 3.1 Emission
Radiated airborne sound from a certain sound source (the machine under test). Note 3: The noise emission characterization quantity can be included in the product label or product manual. The basic noise emission characterization quantity is the sound power level of the sound source and the emission sound pressure level of the working position near the sound source and other specified positions (if any). 3.2 Emission sound pressure (p) emission sound pressure The sound pressure at a specified position near the sound source working under the specified installation and operating conditions on a reflecting plane. It does not include the influence of background noise and other sound reflections outside the reflecting surface allowed by this test method, unit Pa. 3.3 Emission sound pressure level (L,) emission sound pressure level The logarithm to the base 10 of the ratio of the square of the emission sound pressure p2(t) to the square of the reference sound pressure p multiplied by 10. The measurement is carried out using the time weighting and frequency weighting specified in GB/T 3785, and the unit is dB. The reference sound pressure is 20μPa. p2(t) represents the change of the square of the effective value of the sound pressure over time. Note 4: For example; F time-weighted maximum A-weighted emission sound pressure level LrAFmC-weighted peak emission sound pressure level LsC.pek. The emission sound pressure level should be measured at the specified position, and its position should comply with the test procedures of the machine series; if there is no corresponding test procedure, the method used should comply with the provisions of the GB/T17248 series of standards. 3.3.1 Time-averaged emission sound pressure level (Lpgr) time-averaged emission sound pressure level Within the measurement time T, the mean square sound pressure of a noise signal that varies with time is equal to the square of the sound pressure of the continuous steady-state sound within the same time. The sound pressure level of the continuous steady-state sound is the time-averaged emission sound pressure level, in dB. It is expressed by formula (1): 1r p()dt
Lrar = 10lg. p
A weighted time-averaged emission sound pressure level is expressed as LpAeT, which can be abbreviated as LpA. Its measuring instrument should meet the requirements of GB/T 17181 standard.
Note 5: In general, since the time-averaged emission sound pressure level must be measured within a certain measurement time, the subscripts eq and T can be omitted. Note 6: Formula (1) is the same as the expression of the environmental noise characterization quantity "equivalent (continuous) sound pressure level" defined in GB/T3222 standard. However, the emission quantity defined in this standard is used to characterize the noise emission of the machine under test, and it is assumed that standard measurement and operating conditions and a limited acoustic environment are used for measurement. 3.3.2 Peak emission sound pressure level (Lppe) Peak emission sound pressure level The maximum transient value of the emission sound pressure level measured within an operating cycle, in dB. 3.3.3 Single-event emission sound pressure level (Lp,1) Single-event emission sound pressure level The time-integrated emission sound pressure level of a single isolated acoustic event within the specified measurement time T (normalized to T with T.=1s), in dB. Expressed by formula (2):
Lpl =10lg]. p
= Lmar + 10lg T.
Note 7: The above formula is the same as the expression of the similar environmental noise description quantity "exposure level". However, the emission quantity defined in this standard is used to characterize the characteristics of the noise source and assumes that a limited acoustic environment is used for measurement. 3.4 Impulsive noise index (impulsiveness) This index is used to characterize the impulse characteristics of the noise emitted by the sound source (see Appendix C), unit dB. 3.5 Free field over a reflecting plane The sound field in an isotropic uniform medium in the half space above the infinite, hard plane where the machine under test is located. 3.6 Work station, operator's position The position near the machine under test, designated for the operator. 3.7 Operator operator
GB/T 17248.3—1999
A person engaged in work tasks related to the machine near the machine under test. 3.8 Specified position specified position A position relative to the machine, including but not limited to the operator's position. The position may be a single fixed point, or a number of points on a path, or a number of points on a surface at a specified distance from the machine. If there is a relevant test procedure, it shall be stated in it. NOTE 8 A specified position near the working position or near an unattended machine may be considered a "bystander position". 3.9 operational period The time interval for the machine under test to complete a specified process (e.g. the time required for a dishwasher to complete washing, rinsing or drying). 3.10 operational cycle The time required for the machine under test to complete a working cycle, in which the operating periods appear in a specified sequence, each operating period is associated with a specific process, and the specific process may occur only once in an operating cycle, or it may be repeated multiple times (e.g. the process of a dishwasher from washing to rinsing to drying).
3. 11 measurement time interval A part or multiple of an operating period or operating cycle. During this time, the emission sound pressure level is measured or the maximum emission sound pressure level is obtained. 3.12 Time history
A continuous record of the emission sound pressure level as a function of time in one or more operating periods of the operating cycle. 3.13 Background noise The noise of all sound sources other than the machine under test. Note 9: Background noise should include air noise, structure-borne noise and instrument electrical noise. 3.14 Background noise level background noise level The sound pressure level measured when the machine under test is not working, in dB. 3.15 Background noise correction value (K,) background noise correction This correction value is used to indicate the influence of background noise on the emission sound pressure level at the specified position of the machine under test. K, is related to the frequency, in dB. The correction item K1A in the A-weighted case is obtained from the A-weighted measurement value. 3.16 Environmental correction value (K) environmental indicator This correction value is used to indicate the influence of sound reflection or sound absorption on the surface sound pressure level. K, is related to the frequency, in dB. In the A-weighted case, it is expressed as K2A (see GB/T3767, GB/T 3768). 3.17 Local environmental correction value (K3) local environmental correction This correction value is used to indicate the influence of reflected sound on the emission sound pressure level at the specified position of the machine under test (such as the working position), in dB. K: is related to the frequency and position. In the A-weighted case, it is expressed as K3A. 3.18 Typical distance (a) The distance from a specified position to the nearest main sound source of the machine. If the main sound source of the machine cannot be determined, the distance from the specified position plate to the nearest part of the machine is selected as a.
4 Measurement uncertainty
The single value of the emission sound pressure level of the noise source measured by the method specified in this standard may differ from the true value of the corresponding quantity at a fixed position within the measurement uncertainty range. The measurement uncertainty of the emission sound pressure level is caused by several factors that affect its results, some of which are related to the test environment conditions and the other part is related to the test technology. The measurement uncertainty depends on the standard deviation of the reproducibility and the expected confidence. In order to determine the standard deviation of the reproducibility of the emission sound pressure level at each position, a large amount of measurement data must be obtained. In addition, for many different types of machines and equipment to which this standard applies, the range of standard deviation may be large. Therefore, it is impossible to provide widely applicable data. Here, only data related to individual types of noise sources are provided as a reference for noise test procedures.
Since the measurement is carried out under the condition that the environmental conditions are not easy to control, the measurement accuracy of the method specified in this standard is lower than that of the engineering method specified in GB/T17248.2. 375
GB/T 17248.3—1999
Note 10: The method given in this standard generally underestimates the size of the local environmental correction value K: and limits it to less than 2.5dB. Therefore, the emission sound pressure level obtained by this method is often greater than the emission sound pressure level measured by GB/T17248.2. Since the local environmental correction value is limited to 2.5dB, detailed information on the accuracy of this method cannot be given. Assuming that the test is completed in a similar acoustic environment, for a noise source with a relatively flat spectrum in the frequency range of 100 to 10000Hz, the reproducibility standard deviation is not greater than 5dB (excluding the influence of changes in operating and installation conditions). The reproducibility standard deviation given above is the maximum value, but for a certain machine series, this value may be smaller.
Note 11: GB/T17248.5 gives another more accurate method for determining K:. The requirements for K. depend on the method used to determine LpA. 5 Measuring instruments
The instrument system including microphone and cable shall meet the requirements of type 2 or above sound level meter specified in GB/T3785; when using an integrating average sound level meter, it shall meet the requirements of type 2 or above integrating average sound level meter specified in GB/T17181. Before and after each measurement, the microphone shall be calibrated with a sound calibrator with an accuracy better than ±0.3dB (grade 1 accuracy specified in GB/T15173) to calibrate the entire measurement system at one or more frequencies within the test frequency range. The sound calibrator shall be calibrated once a year in accordance with the requirements of GB/T15173. The instrument system shall be calibrated at least once every two years in accordance with the requirements of GB/T3785 (if an integrating average system is used, it shall be calibrated in accordance with the requirements of GB/T17181). The last calibration date of the calibration in accordance with the national standard shall be recorded. 6 Test environment
6.1 Overview
This standard applies to any environment that meets the conditions specified in 6.2 and the background noise is appropriately corrected according to 6.4. 6.2 Test environment applicability criteria
The environmental correction value KzA of the test environment (as defined in GB/T3768) is used to characterize the degree to which the test environment deviates from the ideal, free-field condition. For this standard, the environmental correction value K2A should not exceed 7 dB. 6.3 Enclosed working position
When the operator is located in a closed operating room or an enclosed space away from the machine under test, since the operating room or enclosed space is an integral part of the machine under test. Therefore, the sound reflection in the operating room or enclosed space is considered to have an impact on the emission sound pressure level, and environmental correction is not allowed.
During the noise emission measurement, the doors and windows of the operating room or enclosed space should be opened or closed in accordance with the relevant provisions of the noise test procedure for the machine equipment.
If the machine's working position or spectator position is in the operator's room or workshop (for maintenance), the noise test procedure should specify an additional "customary" working position or spectator position outside the operator's room or workshop of the machine under test. 6.4 Background noise correction criteria
At the microphone position, the background noise measured as the weighted sound pressure level or in each measurement band (including wind noise at the microphone) should be at least 3 dB lower than the machine sound level or frequency band sound level under test (preferably lower than 10 dB). The background noise correction value is given by formula (3): K, = -— 10lg(1— 10-0.14)
Where: AL is the difference in sound pressure level measured at the specified position when the machine under test is turned on and off, in dB. For this standard, if △L>10dB, K0 is specified; if △L<3dB (i.e. KiA>3dB), the measurement is invalid. K1 should be determined for each microphone position. 6.5 Environmental conditions during measurement
Environmental conditions may have an adverse effect on the microphone used for measurement. The microphone and its position should be properly selected to avoid the effects of strong electric and magnetic fields, strong winds, high and low temperatures, exhaust shock from the machine being measured, etc. When measuring outdoors, the wind speed should be less than 6 m/s (equivalent to level 4 wind) and a wind shield should be used. Note 12: IS () 11202 does not make specific provisions for wind speed. Considering the operability of actual measurement and the national standard that the wind speed is generally less than 6 m/s for outdoor measurement (see GB/T 3768).
6.6 Local environmental correction value
GB/T 17248.3—1999
Appendix A gives the steps for determining the local environmental correction value K:, which takes into account the influence of reflected sound on the emitted sound pressure level at a specified location. The method given in Appendix A requires information on the acoustic characteristics of the test room. This method generally underestimates the size of K:. When A-weighted, the local environment correction value K3A should not exceed 2.5dB. Note 13: If the limit of 2.5dB is exceeded, the accuracy of the result will be reduced. However, even so, this result should be recorded, which is helpful to determine the upper limit of the emission sound pressure level at the specified location.
7 Test quantity
In the specified operating period or operating cycle of the machine under test, the basic test quantity at each specified location is: A-weighted sound pressure level LpA (the apostrophe indicates the measured value) w-C-weighted peak sound pressure level LpC.peak
Note 14: For some applications, it is not necessary to measure the C-weighted peak sound pressure level (see ISO4871:1996 Chapter 5 Note 19). 8 Quantified quantity
In order to obtain the emission sound pressure level at the specified location, except for the peak sound pressure level LC,pek, which is not allowed to be corrected, the background noise correction K and the local environment correction K should be used. Correct the measured sound pressure level. The correction values ​​K, and K3 are related to the frequency weighting of the measured radiated sound pressure level. Weighting for A: LpA L pA — KiA -- K3A
Where: Apostrophes indicate measured values, and no apostrophes indicate emission values. For specified locations within the enclosed space defined in 6.3, environmental corrections are not allowed. *+ (4)
Note 15: If the machine under test produces isolated single-event noise, the single-event emission sound pressure level Lp1 at the specified location can be determined (see 3.3.3). 9 Installation and operation of the machine under test
9.1 Overview
The installation and operation of the machine under test have a great influence on the emission sound pressure level at the specified location. This chapter specifies the relevant installation and operating conditions to ensure that the changes in the emission noise caused by the installation and operation of the machine under test are minimized. For the machine under test, if there is a noise test procedure, it should be followed. The same installation and operating conditions should be used to determine the emission sound pressure level and sound power level. The noise test procedure for the machine equipment should provide detailed information on its installation, placement and operating conditions. Note 16: For equipment used on the table, the noise test procedure may not require the same installation, placement and operating conditions. When determining the sound power level, the equipment can be placed on the floor.
For large machines, the installation and operating conditions of the machine's components, assemblies, auxiliary equipment, power sources, etc. must be determined. 9.2 Location of sound sources
The machine under test should be installed in one or more positions on the reflective surface according to normal use. The machine under test should be away from any walls, ceilings or other reflective surfaces.
Note 17: For some machines, the typical installation conditions include: two or more reflecting surfaces (such as wall-mounted devices) with free space (such as elevators) or an opening in a reflecting surface (sound radiation appears on both sides of the vertical plane). The detailed installation conditions shall be based on this standard and relevant noise test procedures.
9.3 Sound source installation
In many cases, the noise emission at a specified location of the machine under test is related to the supporting installation conditions of the machine. When the machine has typical installation conditions, such conditions should be used and simulated as much as possible. If typical installation conditions are not available or these conditions cannot be used for testing, care should be taken to avoid changes in the machine's radiated noise caused by the installation system used for testing, and measures should be taken to try to reduce the radiated noise of the equipment installation structure. Many small machines, although they radiate little low-frequency sound themselves, due to installation reasons, their vibration energy is transferred to a large surface that is sufficient to effectively radiate energy, thereby radiating more low-frequency sound. If possible, resilient supports should be inserted between the machine under test and its base surface to minimize the transmission of vibrations to the base and the response of the sound source. In this case, the mounting base should have a high enough mechanical impedance to prevent additional sound radiation due to large amplitude vibrations. However, when the typical installation environment of the machine under test can only be resilient, resilient mounting should be used.
NOTE 18: Coupling conditions (such as between the prime mover and the driven machine) may also have a significant effect on the sound radiation of the sound source under test. 9.3.1 Hand-held mechanical equipment
This mechanical equipment should be hand-held and suspended in the air so that structure-borne sound is not transmitted through any accessories that are not part of the machine under test. If the machine under test requires a support when in operation, the support structure should be small enough to be considered as part of the machine under test and described in the noise test procedures (if any).
9.3.2 Foundation-supported and wall-mounted mechanical equipment Such mechanical equipment should be placed on a reflecting surface (acoustically hard surface such as floor or wall). For machines with foundations installed in front of a wall, the machine equipment should be installed on an acoustically hard surface in front of an acoustically hard wall. Table-type machines should be placed on a table or stand in accordance with the operating requirements of the noise test procedure for the machine under test. The distance between the table or stand and any sound-absorbing surface in the test room should be at least 1.5m. Such machines should be placed in the center of the standard test table. The design of the test table is shown in Appendix B. 9.4 Auxiliary equipment
Any cable ducts, air ducts, etc. connected to the machine under test should not radiate significant sound energy into the test environment. All auxiliary equipment that is not part of the machine under test but is necessary for the operation of the machine under test should be placed outside the test environment as far as possible; if this is not possible, the auxiliary equipment should be included in the test device and the operating conditions should be described in the test report. 9.5 Operation of the machine during the test
During the noise measurement, for the machine equipment family to which the machine under test belongs, if there is a noise test procedure, the operating conditions specified in the test procedure should be used. If there is no test procedure, the machine under test should be operated in normal use as far as possible. In this case, one or more of the following operating conditions should be selected:
a) under specified load and operating conditions;
b) under full load conditions;
c) under no load (no load) conditions;
d) under working conditions corresponding to the maximum noise output during normal use; e) under simulated load conditions of the specified operating conditions; f) under conditions with a characteristic operating cycle. The emission sound pressure level at the specified location should be determined under any expected operating conditions (such as temperature, humidity, device speed, etc.). These test conditions should be selected in advance and remain unchanged during the test. Before any noise measurement is made, the machine under test should be in the expected set of operating conditions. If the noise emission also depends on other operating parameters (such as: type of processed material or tool model), in this case, appropriate parameters should be selected as far as possible to minimize the change in sound radiation and be in a typical sound radiation state. For some special tests, one or more conditions can be appropriately set to ensure that the noise emission of the same series of machines and equipment has a high reproducibility and that the operating conditions are the most common and typical for the machine and equipment series. These operating conditions should be specified in the professional noise test procedures.
If simulated operating conditions are used, those conditions shall be selected that give a representative sound pressure level at a specified location under normal use of the machine under test.
In special cases, the results of several operating conditions may be combined by energy averaging taking into account the different time components, thus obtaining the result under the main operating conditions (see 10.1). The operating conditions of the machine under test during the noise measurement shall be fully described in the test report. 10 Measurement
10.1 Measurement time
10.1.1 Overview
GB/T 17248.3—1999
The principle of selecting the measurement time is that the time characteristics of the emission sound pressure level at a specified location and the noise emission (if required by the regulations) can be determined under the specified operating conditions.
For a given sound source under test, the measurement time consists of a series of sub-measurement times T, each of which corresponds to a specified operating period of the sound source. In this case, it can usually be described by a single emission sound pressure level, which can be averaged according to formula (5) for the A-weighted emission sound pressure level of each sub-measurement time:
[T:×101pA Ta
LA = 10lg|—
where, T—total measurement time, S;
T,—sub-measurement time, ;
N—total number of sub-measurement times or operating periods; LpA,T(i)—A-weighted emission sound pressure level within the sub-measurement time T:, dB. · (5)
For machines and equipment with a specified operating cycle, it is usually necessary to extend the measurement time to an integer multiple of the continuous operating cycle. The measurement time is only related to the operating period for which the emission sound pressure level and the time characteristics of the sound emission (if required) are expected. The value of the measurement time, the possible required sub-measurement time and the number of operating cycles included in the measurement time should comply with the noise test procedures for the machine under test (if any). In any case, these values ​​are the same as those specified for determining the sound power level of the machine under test. 10.1.2 Steady-state noise
If the noise emission at the specified location is steady-state noise under the specified operating conditions (see GB/T14259 and ISO12001), the measurement time shall be at least 15 s.
10.1.3 Non-steady-state noise
If the noise emission at the specified location is non-steady-state noise under the specified operating conditions, the measurement time and the operating period of the machine under test shall be specified in detail in the test results and reported. If there is a noise test procedure, the measurement time and the operating period of the machine under test are usually specified in the test procedure.
10.1.4 Frequency band measurement
If octave or 1/3 octave band measurements are performed, the minimum measurement observation time shall be 30 s for bands with a center frequency of 160 Hz or less, and 15 s for bands with a center frequency of 200 Hz or more. 10.2 Measurement procedure
10.2.1 Overview
The emission sound pressure level shall be measured over a typical operating period of the machine under test (see 10.1) Measure and obtain the emission sound pressure level reading at the specified location.
Usually, the emission sound pressure level is measured using an integrating average sound level meter that meets the requirements of GB/T17181 (see Chapter 5). If it is known that the fluctuation of the sound pressure level measured using the time-weighted characteristic "S" is less than ±1dB, a Type 2 sound level meter that meets the requirements of GB/T3785 can be used. In this case, the sound pressure level can be taken as the average of the maximum and minimum sound levels measured using the time-weighted characteristic "S" during the measurement observation period. 10.2.2 Repeatability of measurement
In order to reduce the uncertainty in determining the emission sound pressure level at a specified location, it is necessary to repeat multiple measurements of the machine equipment in accordance with the provisions of the noise test procedure for the machine being tested. If there is a noise test procedure, the measurement value (i.e., the average or maximum value) adopted after repeated measurements should be taken in accordance with the provisions of the test procedure. Repeated measurements include the following steps: a) if practicable, turn the machine under test off and on again; b) remove the microphone and place it again in the specified position; c) measure again in the same environment, under the same installation and operating conditions, using the same measuring instrument and at the same measurement time.
10.2.3 Measurement process of impulse noise
GB/T17248.3—1999
If the acoustic emission is an impulse sound (as described in Appendix C), the instrument should have a sufficiently large dynamic range when measuring the emission sound pressure level, and the sound level meter should be equipped with an overload indicator.
To measure the time characteristics of impulse acoustic emission (i.e. many peaks), in addition to the repeated measurement process described in 10.2.2 above, the measurement time should include at least 10 pulses. If the noise test procedure has other provisions, it shall be carried out in accordance with the test procedure. Unless the peak value is measured, the final measurement is generally taken as the average value. When measuring the peak value, the maximum value of each peak value should be retained. If the noise test procedure specifies a more precise measurement process, that process shall be used. If the machine under test produces isolated single-event noise, the single-event emission sound pressure level Lp1 at the working position shall be determined (see 3.3.3).
To determine whether the sound emission contains an impulse component, a measurement method given in Appendix C may be used. 11 Microphone position
11.1 Overview
The specific measurement position can be selected from the various positions described in 11.2, 11.3, 11.4 or 11.5. The orientation of the microphone should make the sound incident direction consistent with the direction of the microphone reference axis specified by the manufacturer (meeting the requirements of GB/T3785 or GB/T17181 respectively). If possible, no one should be present next to the machine when measuring the emission sound pressure level, and the microphone should be pointed at the main sound source.
If the operator is present, the operator should not wear clothing with abnormal sound absorption characteristics or any hat or scarf (other than a protective helmet required for safety reasons, or a wind shield or bracket for positioning the microphone), which will affect the noise measurement. If the operator is present, the microphone should be located on the operator's head, 0.20 m ± 0.02 m to one side of the center plane of the line between the two eyes, with its axis parallel to the operator's line of sight and on the side with the higher measured A-weighted sound pressure level LA. NOTE 19: If the measured sound pressure level is highly dependent on the position, it is recommended to use the spatial average of several positions within a small volume range located at the center of the specified position.
Unless otherwise specified in the noise test procedure, the operator position shall be as specified in 11.2 to 11.5. 11.2 Microphone position for seated operators If the operator is not present and the seat is connected to the machine under test, the microphone shall be located 0.8 m ± 0.05 m above the center of the seat plane unless the noise test procedure specifically specifies another position. If the operator is not present and the seat is not connected to the machine under test, if there is a noise test procedure, the microphone position should be determined according to the test procedure. If there is no test procedure, it should be noted in the test report. If the operator is present, the seat should be adjusted so that the operator can control comfortably. The distance from the seat plane to the top of the operator's head is determined to be 0.91m±0:05m.
11.3 Microphone position for standing, fixed-position operators If the operator is present during the measurement, 11.1 of this standard applies. If the operator or bystander is not present and the noise test procedure does not specify another position for the standing operator, the microphone position can be defined as a reference point on the ground where the operator usually stands. The reference point is the vertical projection of the center of the operator's head on the ground. The microphone position should be located at a height range of 1.55m±0.075m above the reference point. The noise test procedure (if any) generally specifies the height. 11.4 Microphone positions when the operator moves along a specified path When the operator moves along a specified path near the machine or equipment under test, there should be a sufficient number of microphone positions or movable microphones to determine the sound pressure level along the specified path. The sound pressure level along the specified path can be determined by continuous integration along the length of the path, or by making a sufficient number of measurements at discrete positions or specified time intervals, and then applying formula (5). The reference line is defined as a line segment on the ground along a typical specified path directly below the center of the operator's head. If the noise test procedure does not specify other heights for the moving operator, the microphone should be located at a position directly above the reference line within the range of 1.55m ± 0.075m.1 applies. If the operator or bystander is not present and the noise test procedure does not specify other positions for standing operators, the microphone position can be defined as a reference point on the ground where the operator usually stands. The reference point is the vertical projection of the center of the operator's head on the ground. The microphone position should be located at a height range of 1.55m ± 0.075m above the reference point. The noise test procedure (if any) generally specifies the height. 11.4 Microphone positions when the operator moves along a specified path When the operator moves along a specified path near the machine equipment under test, there should be a sufficient number of microphone positions or movable microphones to determine the sound pressure level along the specified path. The sound pressure level along the specified path can be determined by continuous integration along the length of the path, or by making a sufficient number of measurements at discrete positions or specified time intervals, and then applying equation (5). The reference line is defined as a line segment on the ground directly below the center of the operator's head along a typical specified path. If the noise test procedure does not specify another height for a moving operator, the microphone shall be located within the range of 1.55 m ± 0.075 m directly above the reference line.1 applies. If the operator or bystander is not present and the noise test procedure does not specify other positions for standing operators, the microphone position can be defined as a reference point on the ground where the operator usually stands. The reference point is the vertical projection of the center of the operator's head on the ground. The microphone position should be located at a height range of 1.55m ± 0.075m above the reference point. The noise test procedure (if any) generally specifies the height. 11.4 Microphone positions when the operator moves along a specified path When the operator moves along a specified path near the machine equipment under test, there should be a sufficient number of microphone positions or movable microphones to determine the sound pressure level along the specified path. The sound pressure level along the specified path can be determined by continuous integration along the length of the path, or by making a sufficient number of measurements at discrete positions or specified time intervals, and then applying equation (5). The reference line is defined as a line segment on the ground directly below the center of the operator's head along a typical specified path. If the noise test procedure does not specify another height for a moving operator, the microphone shall be located within the range of 1.55 m ± 0.075 m directly above the reference line.
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