Acoustics--Noise emitted by machinery and equipment--Measurement of emission sound pressure levels at a work station and at other specified positions--Method requiring environmental corrections
Some standard content:
GB/T17248.5—1999
This standard is equivalent to the international standard ISO11204:1995 "Method for measuring the sound pressure level of noise emitted by acoustic machines and equipment at work positions and other designated positions - Environmental correction". This standard is the fifth standard in the GB/T17248.1~17248.5 series of standards, which include: GB/T17248.1 Guidelines for the use of basic standards for determining the sound pressure level of noise emitted by acoustic machines and equipment at work positions and other designated positions
GB/T17248.2
Measurement of the sound pressure level of noise emitted by acoustic machines and equipment at work positions and other designated positions - Engineering method for approximately free field above a reflecting surface Noise emitted by acoustic machines and equipment - Work positions Measurement of emission sound pressure level at working position and other designated positions GB/T17248.31
Simplified on-site method
GB/T17248.4Noise emitted by acoustic machines and equipment is determined by sound power levelEmission sound pressure level at working position and other designated positions
GB/T17248.5Noise emitted by acoustic machines and equipmentMeasurement of emission sound pressure level at working position and other designated positionsEnvironmental correction method
This series of standards specifies various methods for measuring emission noise of machines, 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. Drafting units of this standard: Institute of Acoustics, Chinese Academy of Sciences, Shanghai Institute of Electrical Science. Main drafters of this standard: Chang Yadong, Chen Yeshao, Zhang Ruwei. 395
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ISOForeword
The International Organization for Standardization (ISO) is a worldwide federation of national standardization committees (ISO member states). The formulation of international standards is usually completed by ISO technical committees. Each member state 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 state for voting. The draft international standard requires at least 75% of the votes of the member states to be published as an international standard. International Standard ISO11204:1995 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 are indicative and for reference only. 396
GB/T 17248.5-—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. This standard follows the method specified in GB/T17248.2 (engineering method) except for the following cases: a) On-site measurement is allowed;
b) The specified method is used to determine the local environment correction. The result obtained by this method is similar to the result obtained in the free field above a reflecting surface. The correction term is used to obtain the emission sound pressure level at the specified position (including the working position). If the correction term is less than the specified value, the result meets the engineering grade, otherwise it meets the simple grade. This standard is one of the standards in the GB/T17248.1~17248.5 series, which specifies various methods for measuring the noise emission of machines and equipment or equipment parts. GB/T17248.1 provides guiding principles for how to choose the specific method for measuring the emission sound pressure level of machines and equipment, and provides standard details of various methods for measuring sound power levels. 397
National Standard of the People's Republic of China
Acoustics-Noise emitted by machinery and equipment-Measurement of emission sound pressure levels at a work station and at other specified positions-Method requiring environmental corrections1 Scope
1.1 Overview
GB/T 17248.5—1999
eqv ISO 11204: 1995
This standard specifies a method for measuring the emission sound pressure level at the work station and other specified positions near machinery and equipment in an environment that meets certain conditions.
This standard can also measure the A-weighted, C-weighted peak (if necessary) and band emission sound pressure levels. Note 1: For an overview of the contents of this standard and related series of standards, see Table 1 of GB/T 17248.1. This standard gives a method for determining a local environmental correction (with a maximum permissible value) to be applied to the measured sound pressure level to exclude the effects of reflections from other reflective surfaces than the plane on which the machine is placed. The correction is related to the average sound pressure level on the measurement surface, the sound pressure level measured at the specified position, and the environmental correction or equivalent sound absorption area of the test room. The accuracy level of the measurement (engineering or simplified) depends on the local environmental correction. The working position is the position where the operator is located. It can be located in an open space in the room where the sound source is working, in an operating room fixedly connected to the sound source, or in an enclosed space away from the sound source. The specified positions are located near the machine, whether it is attended or unattended. These positions are sometimes referred to as bystander positions.
This standard specifies the requirements for the test environment. It gives specific instructions for the installation and operation of the machine under test and the selection of microphone positions for the working position and other specified positions. The purpose of the measurement is to compare the performance of different machine equipment units of a given series under specified environmental conditions and uniform installation and operating conditions. The data obtained can also be used for emission sound pressure level noise label marking and verification as specified in GB/T14574.
Note 2: At any given location and given installation and operating conditions related to the machine, the emission sound pressure level measured according to this standard method is generally lower than the sound pressure level of the same machine directly measured in a typical workshop. This is due to the influence of reverberation and other machines. For the calculation method of the sound pressure level near a machine running alone in a workshop, 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 type
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 standard applies to indoor or outdoor environments with one or more reflecting surfaces that meet specific requirements. 1.4 Specified locations
This standard applies to working positions and other specified locations where the emission sound pressure level is to be measured. Approved by the State Administration of Quality and Technical Supervision on March 8, 1999398
Implementation on September 1, 1999
Some examples of locations where measurements can be made are as follows; GB/T 17248.5—1999
a) Working position near the machine being tested, which is the case for many industrial machines and household appliances; b) Working position in the operating room, which is an integral part of the machine being tested. This is the case for many trucks and earth-moving machinery.
c) A working position in a partially or fully enclosed space (or behind a barrier) that is an integral part of the machine equipment provided by the manufacturer.
d) A working position in which the machine being measured is partially or fully enclosed, which is the case for some large industrial machines. e) A position for a bystander who is not responsible for operating the machine. f) Other specified positions, not necessarily working positions or bystander positions; working positions may also be located along a specified path of movement for the operator (see 11.4).
1. 5 Measurement uncertainty
It is not possible to give a widely applicable value for the reproducibility of the emission sound pressure level at the working position. Guidance is given in Chapter 4 of this standard.
2 Referenced standards
The following standards contain provisions that, through reference in this standard, constitute provisions of this standard. At the time of publication of this standard, the versions shown are valid. All standards are subject to revision and parties using this standard should investigate the possibility of using the latest version of the following standards. GB/T3102.7—1993 Acoustic quantities and units (eqvISO31:1992) GB/T 3222—1994 Acoustic environmental noise measurement methods (neqISO 1996-1:1992) GB/T3241-1998 Octave and fractional octave filters (eqvIEC1260:1995) GB/T 3767—1996 Acoustics Sound pressure method for determination of sound power level of noise source Engineering method for approximate free field above reflecting surface (eqy ISO 3744:1994) GB/T 3768—1996 Acoustics Sound pressure method for determination of sound power level of noise source Simple method using envelope measurement surface above reflecting surface (eqv ISO 3746:1995) GB/T3785--1983 Electrical and acoustic properties and test methods of sound level meter GB/T 3947—1996
5 Acoustics TerminologybzxZ.net
GB/T 6881—1986 Acoustics Determination of sound power levels of noise sources Reverberation chamber precision method and engineering method (neqISO 3741～3743:1975)
GB/T 6882—1986 Acoustics
Determination of sound power levels of noise sources Anechoic chamber and semi-anechoic chamber precision method (neqISO3745：1977)
GB/T 14259--1993
Acoustics Standard guide for the measurement of airborne noise and the assessment of its impact on humans (neg ISO2204:1979)
GB/T 14574—1993
GB/T 15173--1994
GB/T 17181-—1997
Acoustics Noise labels for machines and equipment (neqISO4871:1984) Sound calibrator (eqvIEC1014:1989) Integrating average sound level meter (idtIEC804:1985) GB/T17248.11) Determination of noise emitted by acoustic machines and equipment Guidelines for the use of basic standards for emission sound pressure levels at work and other specified locations (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
GB/T 17248.3—1999
Engineering method for approximate free field above a reflecting surface (eqvISO112011995) Noise emitted by machines and equipment - Measurement of emission sound pressure levels at working positions and other specified positions
Simplified field method (eqvISO11202:1995) 1) This standard is to be published soon.
GB/T 17248.5—1999
GB/T17248.4-1998 Acoustics Noise emitted by machines and equipment Determination of the emission sound pressure level at the working position and other specified positions by the sound power level (eqvISO11203:1995) Nominalization and verification of noise emission values of machines and equipment ISO 4871:1996 Acoustics
ISO 7779:1988 Acoustics
-Measurement of airborne sound emitted by computers and business equipment 7 Acoustics - Recommended practices for the design of low-noise workplaces containing machines - Part 3: Sound propagation and noise prediction between workplaces ISO/TR 11690-3:1997
12001:1996 Acoustics
3 Definitions
Noise emitted by machines and equipment
-Drafting of noise test procedures and their proposed criteria 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
Airborne sound radiated by a certain sound source (the machine under test). Note 3: The noise emission characterization quantity can be listed on the product label or product manual. The basic noise emission characterization quantity is the southern power level of the sound source and the emission sound pressure level at the working position and other specified positions near the sound source. , 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 background noise and the influence of other sound reflections outside the reflecting surface allowed by this test method, unit Pa. 3.3 Emission sound pressure level Lpemission sound pressure level The logarithm to the base 10 of the ratio of the square of the emission sound pressure p\(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/T3785, and the unit is dB. The reference sound pressure is 20 μPa. p(t) represents the change of the square of the effective value of the sound pressure over time. Note 4: For example: the maximum A-weighted emission sound pressure level LpAFmax with F time weighting; the C-weighted peak emission sound pressure level Ltc,peak 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 Lpegr 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. Then the sound pressure level of the continuous steady-state sound is the time-averaged emission sound pressure level, in dB. It is expressed as formula (1): pt)dt
LpaT 10lg ].
（1）
A-weighted time-averaged emission sound pressure level is expressed as LAegT, which can be abbreviated as LpA. LpAegT should be measured using an instrument that meets the requirements of GB/T17181.
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/T 3222. 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 the measurement is carried out under standard measurement and operating conditions and a limited acoustic environment. 3.3.2 Peak emission sound pressure level Lp.peak 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.ls single-event emission sound pressure level The time-integrated emission sound pressure level of a single isolated acoustic event within a specified measurement time T (normalized to T.1 s), in dB. Expressed by formula (2):
Lps = 10lg J.
=L mar + 1olg.
· (2)
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 it is assumed that the measurement is carried out under a limited acoustic environment. 400
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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), in dB. 3.5 Free field over a reflecting plane The sound field in an isotropic and homogeneous 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
The person who performs work tasks related to the machine near the machine under test. 3.8 Specified position The position related to the machine, including but not limited to the operator's position. The position can be a single fixed point, or several points on a path, or several points on a surface at a specified distance from the machine. Note 8: A specified position near the work station or near an unattended machine can be used as a "bystander position". 3.9 Operational period The time interval for the tested machine to complete a specified process (e.g. the time required for a dishwasher to complete washing, rinsing or drying).10 Operational cycle The time required for the tested machine to complete a working cycle, in which the various operating periods appear in a specified sequence, each operating period is associated with a specific process, and the specific process may only appear once in an operating cycle, or it may be repeated multiple times (such as the process of a dishwasher from washing to rinsing and then drying).
3.11 Measurement time 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 is obtained in one or more operating periods of the operating cycle. 3.13 Background noise background noise All sound sources other than the tested machine. 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 tested machine is not working, in dB. 3.15 Background noise correction (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 measured machine. K is related to the frequency and the unit is dB. The correction item KIA in the A-weighted case is obtained from the A-weighted measurement value. 3.16 Environmental correction (K,) environmental indicator This correction value is used to indicate the influence of sound reflection or sound absorption on the surface sound pressure level. The unit is dB. K is related to the frequency. In the A-weighted case, it is expressed as K2A (see GB/T3767, GB/T3768). 3.17 Local environmental correction (K) 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 measured machine (such as the working position). The unit is dB. K is related to the frequency and position. In the A-weighted case, it is expressed as K3A. 4 Measurement uncertainty
The single value of the emission sound pressure level of a 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 range of measurement uncertainty. The measurement uncertainty of the emission sound pressure level is caused by several factors that affect the result, some of which are related to the test environment conditions and some to the test technique. 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. Moreover, for many different types of machines and equipment to which this standard applies, the range of standard deviations may be large. Therefore, it is impossible to provide widely applicable data. Only data related to individual types of noise sources are provided here as a reference for noise test procedures.
The method specified in this standard will produce different accuracy, which depends on the specified location and the relevant local environmental correction value. If K3A is less than or equal to 2dB, the accuracy is the engineering level; if K3A is greater than 2dB but less than 7dB, the accuracy is the simple level. Accuracy is related to the location.
For a sound source that emits a relatively "flat" noise spectrum in the frequency range of 100 to 10000Hz, for engineering level measurements, it can be expected that its reproducibility standard deviation value is less than or equal to 2.5dB (here, the effects of changes in operating and installation conditions are not included), while for simple level measurements, it can be expected that its reproducibility standard deviation is less than 5dB. The reproducibility standard deviation given above is the maximum value, but for a certain machine series, this value is smaller. For example: for a series of woodworking machine tools, its reproducibility standard deviation can be equal to 1.0dB. 5 Measuring instruments
The instrument system including microphones and cables should meet the requirements of Type 1 sound level meters specified in GB/T3785; when using an integral average sound level meter, it should meet the requirements of Type 1 integral average sound level meters specified in GB/T17181. For octave and 1/3 octave measurements, the filters used shall meet the requirements of GB/T3241. Before and after each measurement, the microphone shall be calibrated with an acoustic 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 acoustic calibrator shall be metrologically verified once a year in accordance with the requirements of GB/T15173. Every two years, the instrument system shall be metrologically verified at least once in accordance with the requirements of GB/T3785 (if an integral averaging system is used, it shall be metrologically verified in accordance with the requirements of GB/T17181). The last date of metrological verification in accordance with national standards shall be recorded. 6 Test environment
6.1 Overview
Any environment that meets the judgment requirements of 6.2 and excludes the influence of background noise in accordance with the requirements of 6.4 can be measured in accordance with this standard. 6.2 Applicable criteria for test environment
Appendix A of GB/T3767-1996 and GB/T3768--1996 specifies the method for determining the positive value of the environmental value K2A, which is used to characterize the degree to which the test environment deviates from the ideal condition. For this standard, the environmental correction value K2A should not exceed 7dB. 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, it is considered that the sound reflection in the operating room or enclosed space has an impact on the emission sound pressure level, and environmental correction is not allowed.
In 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.
Note 10: Due to the requirements of this standard for instruments and background noise levels, the measurement should meet the engineering grade requirements and accuracy (see GB/T 17248.2). 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 rule
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 6 dB lower than the machine sound level or frequency band sound level under test (preferably lower than 15 dB). The background noise correction value is obtained by formula (3): K —10lg(1— 10-0.14)
.....( 3)
Where: △L—the difference in sound pressure level measured at the specified position when the machine under test is turned on and off. For this standard, if △L>15dB, K1=0 is specified; if △L<6dB (i.e. KiA≥1.3dB), the measurement is invalid according to this standard.
K1 should be determined for each microphone position.102
6.5 Environmental conditions in measurement
GB/T17248.5—1999
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 influence of strong electric and magnetic fields, strong winds, high and low temperatures, and the impact of the exhaust of the machine under test. 6.6 Local environmental correction
Appendix A introduces the method for determining the local environmental correction value K. K: is used to represent the influence of reflected sound on the emitted sound pressure level at a specified position.
The method given in Appendix A requires data from a large number of measurement points near the machine under test, as well as data on the acoustic characteristics of the test room. If K3A does not exceed 7dB, the measurement made in accordance with this standard is valid; if K3A is less than or equal to 2dB, its accuracy is the engineering method level; if K3A is greater than 2dB but less than or equal to 7dB, its accuracy is the simplified method level. 7 Test Quantities
The basic test quantities at each specified position during the specified operating period or operating cycle of the machine under test are: A-weighted sound pressure level L'pA (the apostrophe indicates the measured value); -C-weighted peak sound pressure level LCneak.
Note 11: In accordance with the design requirements of low-noise machines, other frequency weightings or octave or 1/3 octave sound pressure levels, as well as other quantities related to the time history of noise emissions (such as impulse and sound pressure level as a function of time) may also be measured. Note 12: For some applications, it is not necessary to measure the C-weighted peak sound pressure level (see Note 19 of Chapter 5 of IS04871:1996). 8 To be determined
To obtain the emission sound pressure level at a specified location, the measured sound pressure level must use both the background noise correction value K, and the local environment correction value K3. Peak sound pressure level LC.The exception is penk, where corrections are not allowed for bee-value sound pressure levels. The correction terms K, and K: are quantities related to the frequency weighting of the measured sound pressure level, weighted for A: LpA = IA - KiA - K3A
(4)
where: apostrophes indicate measured values, and no apostrophes indicate emission values. For designated locations within an enclosed space as specified in 6.3, environmental corrections are not allowed.
Note 13: If the machine under test produces isolated single-event noise, the single-event emission sound pressure level Lv1s at the designated 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 significant impact on the emission sound pressure level at the designated location. This chapter specifies the relevant installation and operation conditions to ensure that the changes in emission noise caused by the installation and operation of the machine under test are minimized. For the machine equipment series to which the machine under test belongs, if there is a noise test procedure, its relevant provisions should be followed. The same installation and operating conditions should be used for the determination of emission sound pressure levels and sound power levels. The noise test procedures for the relevant machines should provide detailed information on its installation, placement and operating conditions. NOTE 14: For equipment used on tabletops, the noise test procedures 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 noise test procedures are particularly important, which list in detail the parts, assemblies, auxiliary equipment, power sources, etc. of the machine under test.
9.2 Location of sound sources
The machine under test should be installed in one or more locations on the reflecting surface as in normal use. The machine under test should be away from any walls, ceilings or other reflecting surfaces.
NOTE 15: For some machines, typical installation conditions include: two or more reflecting surfaces (such as: close-mounted devices) or 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 should be based on this standard and the relevant noise test procedures (if any).
9.3 Installation of sound source
GB/T 17248.5—1999
In many cases, the noise emission at a specified location of the machine under test is related to the support or installation conditions of the machine. When the machine has typical installation conditions, such conditions should be used and simulated if 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 the test, 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 sufficient to effectively radiate energy, thereby radiating more low-frequency sound. If possible, elastic support should be added between the machine under test and its base surface to minimize the transmission of vibration to the base and the response of the sound source. In this case, the mounting base should have a sufficiently high force impedance to prevent additional sound radiation due to excessive vibration. However, when the typical installation environment of the machine under test can only be elastic mounting, elastic mounting should be used.
Note 16: Coupling conditions (such as between the prime mover and the driven machine) may also have a significant impact on the sound radiation of the sound source under test. 9.3.1 Handheld mechanical equipment
This mechanical equipment should be handheld and suspended in the air so that the 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 working; the structure of the support should be small and can be regarded as part of the machine under test and described in the relevant noise test regulations (if any).
9.3.2 Foundation-supported and wall-mounted mechanical equipment Such mechanical equipment should be placed on a reflecting plane (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-top mechanical equipment should be placed on a table or stand in accordance with the operating requirements of the noise test regulations for the machine under test. The distance from the table or stand to any sound-absorbing surface in the test room should be at least 1.5m. Such mechanical equipment should be placed in the center above the standard push test table. For the design of the test bench, see Appendix B. 9.4 Auxiliary equipment
Any cable ducts, air ducts, etc. connected to the machine under test should not radiate obvious sound energy to the test environment. If possible, 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; 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 series 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 if 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 (idle) conditions;
d) under working conditions corresponding to the maximum noise output during normal use; e) under simulated load conditions with carefully 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 changes in sound radiation and to be in typical operating conditions. For some special tests, one or more conditions can be set appropriately to ensure that the noise emission of the same series of machines and equipment has a good reproducibility and the operating conditions are the most common and typical for the machine and equipment series. These operating conditions shall be defined in the professional noise test procedure.
GB/T 17248.5--1999
If simulated operating conditions are used, those conditions shall be selected that give the emission sound pressure level at the specified location representative of the machine under normal use.
In special cases, the results of several operating conditions may be combined by the energy averaging method to give the results under the main operating conditions (see 10.1).
During the noise measurement, the operating conditions of the machine under test shall be fully described in the test report. 10 Measurement
10.1 Measurement time
10.1.1 Overview
The measurement time shall be selected so that the emission sound pressure level at the specified location and the temporal characteristics of 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:
ET: X 100.11.r6)
LpA 10lgl
Where: T—total measurement time, s;
T,—sub-measurement time, s;
N total number of sub-measurement times or operating periods; LpA,T(G)—A-weighted emission sound pressure level within 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 acoustic emission time characteristics (if required) are expected to be obtained. The measurement time, the possible sub-measurement time and the number of operating cycles included in the measurement time should comply with the professional noise test procedures for the machine under test. 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 defined in detail in the test results and reported. If there is a relevant 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, for the center frequency 160.Hz and below, the minimum measurement observation time shall be 30s, while for the frequency band with a center frequency of 200Hz and above, the minimum measurement observation time shall be 15s. 10.2 Measurement process
10.2.1 Overview
The emission sound pressure level shall be measured during a typical operating period of the machine under test (see 10.1), and the emission sound pressure level reading shall be measured at the specified position.
Usually, an integrating average sound level meter that meets the requirements of GB/T17181 is used to measure the emission sound pressure level (see Chapter 5). If it is known that the sound pressure level fluctuation measured with the time-weighted characteristic \S\ is less than ±1dB, a conventional 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 according to the time-weighted characteristic "S" during the measurement observation period. 405
10.2.2 Repeatability of measurement
GB/T17248.5--1999
In order to reduce the uncertainty of determining the emission sound pressure level at a specified location, it is necessary to repeat the measurement of the machine equipment several times in accordance with the provisions of the noise test procedure of the machine under test. If there is a noise test procedure, the measurement value (i.e. 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 processes: a) if feasible, turn off and turn on the machine under test again; b) remove the microphone and place it again in the specified location; c) measure again under the same environmental conditions, 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
If the sound emission is an impulse sound (as described in Appendix C), when measuring the emission sound pressure level, the instrument should have a sufficiently large dynamic range and the sound level meter should be equipped with an overload indicator.
To measure the time characteristics of pulsed acoustic emissions (i.e. many peaks), the measurement time shall include at least 10 pulses in addition to the repeated measurement process described in 10.2.2 above. If the noise test procedure has other provisions, the test procedure shall be followed. The measurement value is usually the average value. When measuring the peak value, the maximum value of each peak value is taken. If a more accurate measurement process is specified in the noise test procedure, it shall be used. If the machine under test produces isolated single-event noise, the single-event emission sound pressure level Lp.1s at the working position shall be determined (see 3.3.3).
To determine whether the acoustic emission contains an impulse component, one of the measurement methods 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 microphone should be oriented so that the sound emission direction is 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 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 (not a protective helmet required for safety reasons, or a windshield or bracket for fixing the microphone), which will affect the noise measurement. If the operator is present, the microphone should be located on the operator's head, 0.20m ± 0.02m 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 located on the side with the higher A-weighted sound pressure level L,A. Note 17: 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 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 states another position. If the operator is not present and the seat is not connected to the machine under test, the microphone position shall be determined in accordance with the procedure if there is a noise test procedure. If there is no noise test procedure, this shall be noted in the test report. If the operator is present, adjust the seat so that the operator can exercise control comfortably. The distance from the seat plane to the top of the operator's head is set at 0.91 m ± 0.05 m.
11.3 Microphone Position for Standing, Fixed-Position Operators The operator is present during the measurement and 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 a standing operator, the microphone position can be defined as the reference point on the ground where the operator normally 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. 40605m 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 in accordance with the procedure. If there is no noise test procedure, it should be noted in the test report. If the operator is present, adjust the seat so that the operator can comfortably control. The distance from the seat plane to the top of the operator's head is determined to be 0.91 m±0.05 m.
11.3 Microphone position for standing, fixed-position operators The operator is present during the measurement and 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 the reference point position on the ground where the operator usually stands. The reference point is the vertical projection point 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. 40605m 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 in accordance with the procedure. If there is no noise test procedure, it should be noted in the test report. If the operator is present, adjust the seat so that the operator can comfortably control. The distance from the seat plane to the top of the operator's head is determined to be 0.91 m±0.05 m.
11.3 Microphone position for standing, fixed-position operators The operator is present during the measurement and 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 the reference point position on the ground where the operator usually stands. The reference point is the vertical projection point 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. 406
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