This standard specifies an engineering method: determination of the sound power level of a large multi-noise source plant, which is related to the evaluation of its ambient sound pressure level. These sound power levels can be used in prediction models for such evaluation. This method is limited to large plants with multiple noise sources (combinations of individual sound sources), whose main dimensions are located in the horizontal plane and whose noise radiation is basically uniform in all horizontal directions. Unweighted sound pressure levels are measured in octave bands. The sound sources to which this standard applies may be radiated broadband noise, narrowband noise, discrete pure tones, repetitive impulse noise and combinations of these components. GB/T 20246-2006 Acoustics Engineering method for determination of sound power levels of multi-noise source plants for evaluation of ambient sound pressure levels GB/T20246-2006 Standard download decompression password: www.bzxz.net
This standard specifies an engineering method: determination of the sound power level of a large multi-noise source plant, which is related to the evaluation of its ambient sound pressure level. These sound power levels can be used in prediction models for such evaluation. This method is limited to large factories with multiple noise sources (combinations of individual sound sources), whose main dimensions are located in the horizontal plane and whose noise radiation is basically consistent in all horizontal directions. The unweighted sound pressure level is measured in octave bands. The sound sources to which this standard applies may be radiated broadband noise, narrowband noise, discrete pure tones, repetitive impulse noise, and combinations of these components.

ICS17.140
National Standard of the People's Republic of China
GB/T 20246—2006
Acoustics-Determination of sound power levels of multisource industrial plantsfor evaluation of sound pressure levels in the environment---Engineering method(ISO 8297:1994,MOD)
Published on 2006-05-08
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China Administration of Standardization of the People's Republic of China
Implementation on 2006-11-01
1 Scope
Normative references
Terms and definitions
t||General description of measurement methods
Acoustic environment
Measuring instruments||t t||8 Factory operating conditions
Calculation of sound power level for evaluating sound pressure level in the environment, 10
Noise sources significantly higher than the characteristic height of the factory…Report content
GB/T20246--2006
GB/T20246-2006
This standard is modified and adopted ISO8297:1994 "Acoustics Engineering Method for Determination of Sound Power Level in Multiple Noise Source Factories for Evaluation of Environmental Sound Pressure Level".
When modifying and adopting standard ISO8297:1994, this standard omits the references in Appendix A of the original text. This standard is proposed by the Chinese Academy of Sciences.
This standard is under the jurisdiction of the National Technical Committee for Acoustics Standardization (SAC/TC17). Drafting units of this standard: China Machinery International Engineering Design and Research Institute, Dalian Mingri Environmental Engineering Co., Ltd. The main drafters of this standard are: Wang Daolu, Wang Honghui, Wu Daozhong, Zhou Hong, Xie Lixiang, He Wenxue.
GB/T 20246-2006
0.1 This standard specifies an engineering method for determining the sound power level of a multi-noise source factory, which is related to the noise evaluation at various points in the factory's surrounding environment. Its basic principle is to measure the sound pressure level on a closed path (measurement contour line) around the factory and determine the corresponding measurement surface area.
This method is applicable to factories and other large sound sources with multiple noise sources under any specified operating conditions, and the radiation of these sound sources in all horizontal directions is basically the same. The method described in this standard meets the general requirements of GB/T14259---1993. 0.2 The data obtained by this standard are suitable for the following purposes: to calculate the sound pressure level at given points around the factory under specified climatic conditions, the distance from these points to the geometric center of the factory area is at least 1.5 times the maximum linear dimension of the factory area (see Figure 1), and all the individual sound sources in the factory area can be regarded as a single point sound source at the geometric center of the factory; to determine the contribution of industrial areas or specific parts of such areas to the sound pressure level at a given point in the environment; 6) to compare different sound sources (complete factories or composed facilities) according to their sound power; to monitor the noise radiation of the factory.
1 Scope
1.1 General
Acoustics Engineering method for determination of sound power levels in plants with multiple sound sources for evaluation of ambient sound pressure levels
GB/T 20246—2006
This standard specifies an engineering method (level 2 as defined in GB/T14259-1993): determination of the sound power levels of large plants with multiple sound sources, which are related to the evaluation of their ambient sound pressure levels. These sound power levels can be used in prediction models for such evaluations. This method is limited to large plants with multiple noise sources (combinations of individual sound sources), whose main dimensions are located in the horizontal plane and whose noise radiation is essentially uniform in all horizontal directions. The unweighted sound pressure level is measured in octave bands.
The results are expressed in octave band sound power levels and, if necessary, in A-weighted sound power levels. 1.2 Type and size of noise sources
This method can be used in industrial areas where most of the equipment in this area is operated outdoors without buildings, such as petrochemical complexes, quarrying and crushing plants and their pit equipment. This method can also be used for mobile sound sources that operate periodically or continuously, such as towed cable transport lines or cable handling machines. The measurement should be carried out within at least one operating cycle. This method is applicable to plants with a maximum horizontal dimension of 16m to about 320m. 1.3 Type of noise
The sound sources applicable to this standard can be radiated broadband noise, narrowband noise, discrete pure tones, repetitive impulse noise and combinations of these components. The method given is applicable to steady-state noise and statistically stable non-steady-state noise. It is most suitable for broadband steady-state noise and is not suitable for measuring isolated burst sounds.
1.4 Measurement uncertainty
The inherent uncertainty of this method caused by the layout of the plant depends mainly on the ratio of the average distance a between the measuring wheel line and the plant boundary line to the square root of the plant area S, see Table 1. Table 1 Intrinsic uncertainty of this method
a The confidence level of the uncertainty in the table is 95%, and the measurement uncertainty is taken as the maximum value. Uncertainty
These uncertainties caused by the spatial variation of the sound pressure level at different measurement locations should be attributed to the non-uniform distribution of the sound source in the factory, and do not include the uncertainty caused by the difference in noise emission of the sound source during the entire measurement period. Note: When the background noise cannot be corrected according to 9.5.4, the uncertainty will be greater than the value given in Table 1. 2 Normative references
The clauses in the following documents become the clauses of this standard through reference in this standard. For all dated referenced documents, all subsequent amendments (excluding errata) or revisions are not applicable to this standard. However, parties to an agreement based on this standard are encouraged to study whether the latest versions of these documents can be used. For all undated referenced documents, the latest versions apply to this standard. GB/T3222.1 Acoustics Description, measurement and evaluation of environmental noise Part 1: Basic parameters and evaluation methods (idt ISO1996-1) GB/T3240 Frequencies commonly used in acoustic measurements (GB/T3240-1982, neq ISO266:1975) Octave and fractional octave filters (GB/T3241--1998, eqv IEC1260:1995) GB/T3241
GB/T3767 Acoustics Determination of sound power level of noise source by sound pressure method Engineering method for approximate free field above reflecting surface (GB/T3767-1996, eqv ISO 3744 :1994)
GB/T14259—1993 Acoustics Guide to the standard for the measurement of airborne noise and the evaluation of its impact on people (neqISO2204:1979)
GB/T15173-1994 Sound calibrator (eqvIEC60942:1988)IEC61672-1:2002 Electroacoustic sound level meter Part 1: Specification 3 Terms and definitions
The following terms and definitions apply to this standard (see Figure 1). 3.1
Sound power level soundpower level
Lw, LwA
The sound power level of a factory is used to calculate the ambient sound pressure level at a location quite far from the factory, in dB. It is 10 times the base 10 logarithm of the ratio of the given (measured) sound power to the reference sound power. The reference sound power is 1 pW (10~12W). The specific frequency bandwidth should be indicated, for example: octave band sound power level, 1/3 octave band sound power level, etc. The sound power level is marked with the following symbols:
Lw (band sound power level)
LWA (A-weighted sound power level)
Note: The sound power level of a factory measured according to this standard will be different from the sum of the sound power levels of each sound source in the factory. 3.2
Sound pressure level
The ratio of the mean square sound pressure of the sound to the square of the base sound pressure, 10 times the logarithm value to the base 10, expressed in dB. The reference sound pressure is 20 μPa
The specific frequency bandwidth should be indicated, for example: octave band sound pressure level, 1/3 octave band sound pressure level, etc. 3.3
Plant area
The area containing all sound sources in the factory, in m2. 3.4
Measurement area
measurement area
The total area enclosed by the measurement contour, in m2. 3.5
Measurement distance
measurement distance
The distance from the measurement position to the nearest point on the perimeter of the plant, in m. 3.6Www.bzxZ.net
Distance between two measurement positions
distance between measurement positionsDm
The distance between two adjacent measurement positions measured along the measurement contour, in m. Characteristics height of the plantH
The average height of the noise sources within the plant, in m. Equivalent continuous sound pressure level
equivalent continuous sound pressure levelLear
GB/T 20246—2006
A sound that changes with time is equivalent to a continuous steady-state sound within the measurement time interval T, and has the same mean square sound pressure. The value of the sound pressure level of the continuous steady-state sound is the equivalent continuous sound pressure level. The equivalent continuous sound pressure level within the measurement time interval T is given by the following formula; Leq. = 10lgl -
Where:
po——reference sound pressure, po=20 μPa;
The instantaneous sound pressure of the sound signal, in Pascal (Pa). pt
4Symbols
This standard uses the following symbols:
Leq, T:
Measurement distance, in m;
Average measurement distance, in m;
Distance between measurement positions (microphone positions), in m; Microphone height, in m;
Height of the center point of the th noise source, in m, characteristic height of the factory, in m;
th microphone position;
Length of the measurement contour, in m;
Equivalent continuous sound pressure level measured within the measurement time interval T, in dB The average octave-band sound pressure level on the contour line, in dB: the corrected average octave-band sound pressure level along the measurement contour line, in dB; the octave-band sound pressure level at microphone position i on the measurement contour line, in dB; the sound power level of the factory used to evaluate the ambient noise sound pressure level of a given octave band, in dB; the A-weighted sound power level of the factory used to evaluate the ambient noise sound pressure level, in dB; the number of noise sources in the factory;
total number of microphone positions along the measurement contour line
reference sound pressure, po=20 μPa;
Instantaneous sound pressure, in Pa;
Measurement area, in m2;
Reference area (1 m2);
Factory area, in m2;
Sound attenuation coefficient of air, in dB/m; Atmospheric sound attenuation correction term, in dB; Near-field error correction term, in dB;
GB/T20246—2006
ALM:
Correction term for microphone directivity, in dB; Area correction term, in dB;
The angle at which the sensitivity of a directional microphone drops by 3 dB, in dB; The azimuth of the microphone position to the endpoints surrounding the factory area, in dB (see Figure 1). =In azimuth (180°)
Measurement positions
Network Plant area Sp
Measurement area Sm
Distance between measurement positions Dm (Dm ≤ 20)Measurement distance d
Maximum dimension of the plant area
Measurement contour, length 1
Figure 1 General arrangement of measurement positions on a measurement contour around a plant 5 Overview of the measurement method
Draw a closed path of simple shape around the plant area (measurement contour) (see 9.1). The sound pressure level is measured at microphone positions equidistant along the contour and the average sound pressure level is calculated. Error corrections are made for the directivity of the near-field microphone and for air absorption (see 10.5, 10.6, 10.7). Taking into account the area enclosed by the measurement contour, the length of the measurement contour and the height of the microphone, the corresponding correction term ∆Ls for the measurement surface area is calculated (see 10.4) and used to determine the associated sound power level. If the factory contains individual noise sources that are significantly above the ground, they should be treated similarly and additional measurements of the sound power levels of these sources should be made. 6 Acoustic environment
The environment around the microphone position should meet the following requirements as far as possible: a) there should be no reflecting surfaces outside the measurement contour that would affect the sound pressure level measurement; b) the background noise level should be at least 6 dB lower than the sound pressure level to be measured in each frequency band, preferably more than 10 dB lower; c) the wind speed and direction around the measurement contour should not change significantly during the series of measurements. Any deviation from the above requirements should be reported. Note 1: The use of directional microphones can reduce the impact of background noise. Note 2: The main sources of background noise are nearby industrial facilities, road transport and natural sounds. 7 Measuring instruments
7.1 General
The measuring instrument should indicate the sound pressure level in octave bands so that the average value over the entire measurement time can be obtained. It can be obtained by time integration according to the measurement time interval required by GB/T3222.1. If possible, a Class 1 integrating average sound level meter that complies with IEC61672-1:2002 may be used for measurement. If this is not possible and the factory noise is stable, a Class 1 sound level meter that complies with IEC61672-1:2002 may be used for measurement. Note: Using a directional microphone helps to reduce background noise from other directions outside the factory. GB/T20246—2006
If a directional microphone is used, its directional characteristics shall be such that for each octave band, the angle at which the sensitivity decreases by 3dB shall exceed ±30 and be corrected according to 10.6.
7.2 Octave band analyzer
An octave band filter that complies with the requirements of GB/T3241 shall be used. The center frequency of its frequency band shall comply with the provisions of GB/T3240. 7.3 Calibration
The sound calibrator shall comply with the requirements of Class 1 instruments in GB/T15173-1994. During each series of measurements, the calibrator shall be used to calibrate the microphone of the entire measurement system at one or more frequencies within the required measurement frequency. The calibrator shall be calibrated at least once a year, and its output shall not change. In addition, the acoustic and electrical calibration of the instrument system shall be carried out at least once every 2 years within the entire required measurement frequency range. 8 Factory operating conditions
If the factory has different operating modes, each mode shall be measured separately and their sound power levels shall be calculated separately. It should be possible to achieve: the time of each operating mode is long enough and the stability is good enough to complete a complete set of measurements around the measurement contour line. If this cannot be done, the mode can be fully repeated at different measurement locations during successive occurrences. The measurement time interval at each measurement location should be sufficient to include all changes in noise emissions in this mode, including any repetitive impulse noise. 9 Method
9.1 Measurement contour
9.1.1 Requirements for the measurement contour
The microphone positions shall be on a closed path (measurement contour) around the factory area (see Figure 1) and shall meet the following requirements: a) The average measurement distance a shall exceed 0.05VS, or 5 m, whichever is greater; but shall not exceed 0.5S, or 35 m, whichever is smaller.
The average measurement distance α shall be as large as possible within the permissible range of background noise influence; the ratio a//S shall be determined to an accuracy better than ±30%.
b) The azimuth Φ of the factory area, as seen from any point on the measurement contour, shall not be greater than 180 (see Figure 1). c) The distance Dm between adjacent measurement positions on the measurement contour shall not be greater than 2d (see Figure 1). 9.1.2 Determination of the measurement contour line
9.1.2.1 Using the factory floor plan or a suitable map, draw a preliminary measurement contour line around the factory area, which must meet the requirements of 9.1.1a) and 9.1.1b) above. Mark the measurement positions that meet the basic measurement requirements in 9.1.1c) on the contour line. 9.1.2.2 Measure the distance d. from each measurement position to the nearest point on the factory perimeter from the map, and determine the average distance d as follows: d
9.1.2.3 If the first measurement contour line does not meet the requirements of 9.1.1a) and 9.1.1b), another measurement contour line should be selected. 9.1.2.4 The measurement positions are determined as equidistantly as possible along the measurement contour. However, if actual positions must be removed (e.g. due to channels or ditches) or acoustically unacceptable locations occur (e.g. due to walls or buildings), these removed measurement positions are noted. If the number of measurement positions removed exceeds 10%, another measurement contour is selected. NOTE: Generally, one repetition is sufficient to determine a satisfactory measurement contour around the plant. If necessary, further steps should be carried out. A final check of the suitability of the measurement positions is carried out on site. 9.2 Determination of the dimensions of the plant
When a satisfactory measurement contour has been drawn on the plan, the following dimensions shall be determined to an accuracy better than ± 5 %: a) length l of the measurement contour;
b) measurement area Sm;
GB/T 20246—2006
c) characteristic height H of the plant.
The height H, determined by the average height of the noise sources in the factory, can be obtained from the equipment list and the elevation diagram using the following formula: hk
Note: When the factory contains 10 or more sound sources with a height of less than 2m, the average height can be taken as 1m, and their number can be estimated with an accuracy of ±10% in the above sum.
9.3 Microphone height
At each measurement position, the height h of the microphone above the ground can be taken as either the value calculated by the following formula: h = H +0.025 Sm
or 5m. Whichever is greater. If the microphone height cannot be met due to practical reasons or conditions, place the microphone as high as possible above the minimum height of 5m and report this fact. 9.4 Direction of microphone
At each measurement position, the reference direction of the microphone as specified in IEC61672-1:2002 is directed towards the plant area, so that the reference direction is in the horizontal plane and makes an angle of 90° with the measurement contour line. 9.5 Measurement of sound pressure level
9.5.1 General
In the case of steady-state noise, the measurement time at each measurement position shall be long enough to ensure that the measured noise is stable. The measurement time interval in any octave band shall be at least 1 min. In the case of non-steady noise, varying or impulse noise, an integrating average sound level meter shall be used. At each microphone position, the following measurements shall be made: a) During plant operation, the octave band sound pressure levels from 63 Hz to 4000 Hz shall be measured. NOTE: Additional measurements may be made in two octave bands, 31.5 Hz and 8000 Hz. If plant operation can be stopped during the measurement period, the octave band sound pressure levels caused by the background noise shall be measured. If b)
measurements of background noise can be made at different times of the day (e.g. at night), the background noise measurements are valid only if they show no change in the background noise. This should be done by making separate background noise measurements at locations where industrial noise is not prominent, to show whether the background noise has changed.
9.5.2 Measurement with a sound level meter
If the measurement is made with a conventional sound level meter, the time weighting should be set to S (slow). When the indicator on the sound level meter varies by less than 5 dB, the noise can be considered stable for the measurement purposes of this standard and the arithmetic mean of the maximum and minimum levels during the observation period can be taken. If the sound level meter varies by more than 5 dB during the observation period, the noise can be considered unstable and an instrument with an integrating system should be used. 9.5.3 Measurement with an integral system
If an instrument with an integral system is used for measurement, the measured parameter is the stable value Le.r of the equivalent continuous sound pressure level at each measurement position, which will not have a swing greater than ±0.5dB. Use it as the value of Li in item 10.1. 9.5.4 Background noise correction
If the background noise can be measured separately, correct the measured sound pressure level of the factory plus background noise and deduct the background noise according to Table 2. Table 2 Correction values ​​for background noise
Difference between the sound pressure level measured when the plant is in operation and the sound pressure level of the background noise only
In decibels
Correction value to be subtracted from the sound pressure level measured when the plant is in operation, to obtain the sound pressure level obtained when the plant is in operation only Measurement invalid
Difference between the sound pressure level measured when the plant is in operation and the sound pressure level of the background noise only
Table 2 (continued)
GB/T20246-2006
In decibels
Correction value to be subtracted from the sound pressure level measured when the plant is in operation, to obtain the sound pressure level obtained when the plant is in operation only 0.5
If the background noise level cannot be measured separately because the plant cannot be stopped, the measured sound pressure level cannot be corrected. This situation should be reported with a qualitative assessment of the possible error due to the background noise NOTE; In some cases, such as background noise caused by road traffic, the background noise correction can be assessed by calculation. 10 Calculation of sound power level for evaluating sound pressure level in environment Note: For the symbols used in this clause, refer to the explanation in clause 4. 10.1 Step 1
Calculate the average sound pressure level L along the measurement contour line in dB for each octave band using the following formula: L, 10lg[
10.2 Step 2
If any value of L exceeds the average value L, by more than 5 dB, a new measurement contour line with a greater distance from the factory shall be selected. If this is not practicable, all values ​​of L exceeding the average value L, by more than 5 dB shall be replaced by L. L is calculated by the following formula: L = L + 5
10.3 Step 3
Calculate the average sound pressure level I on the second corrected measurement profile, in dB, for each octave band using the following formula: Where:
;10lg[
Li--The octave band sound pressure level corrected according to 10.2 at position i. 10.4 Step 4
Calculate the correction term △Ls caused by the measurement surface area (as defined in GB/T3767), using the following formula: ALs = 10lg
Where:
S. —reference area, S. 1 m2.
10.5Step 5
2Sm+hl
Calculate the near-field error correction term △Lr in dB, which can be calculated by the following formula:△Le = Ig
Note: When the requirements of 9.1 are met, △Lr is expected to be between 0.9dB and -1.9dB. 10.6Step 6
Calculate the microphone directivity correction term △LM in dB, which can be calculated by the following formula:ALM
For a non-directional microphone, △LM=0.
10.7Step 7
Calculate the sound attenuation value △L due to atmospheric absorption, in dB, calculated by the following formula:GB/T 20246—2006
For typical values ​​of α, see Table 3.
AL. = 0. 5α S.
Table 3 Attenuation of the free-propagating sound pressure level due to airborne sound absorption Octave band centre frequency
The values ​​given in Table 3 for the octave bands are valid for a temperature of 15 °C and an average relative humidity of 70 %. If the climatic conditions differ significantly from these, the corresponding air absorption values ​​for the temperature and relative humidity used for the noise measurement shall be used. 10.8 Step 8
Calculate the octave band sound power level Lw in dB from the following formula: Lw = L,+ ALs+ALF+△Lm+△L
If steps 2 and 3 (see 10.2 and 10.3) have been taken, replace L with L;. 10.9 Step 9
If necessary, calculate the A-weighted sound power level LwA in dB using the following formula: LwA = 10lgZ100.1(Lw;+c,)
where:
C—the A-weighted correction for the ith octave band; LWA
—the sum for the entire corresponding octave band.
11 Noise sources significantly above the characteristic height of the plant If the plant contains noise sources that are significantly above the characteristic height, or if these sources are shielded or have directional characteristics, they should not be treated in step 2 (see 10.2) and their sound power levels should be determined in accordance with other appropriate standards. 12 Contents of the report
The test report should state that the sound power levels used to evaluate the sound pressure levels in the environment were obtained in accordance with the requirements and methods of this standard. The report shall include at least the following information: a) the factory and its immediate vicinity, with a diagram of the factory area, the measurement outline and the measurement positions on the measurement outline, including any background noise sources, reflecting structures and objects that may affect the measured sound pressure level; the location of any separately measured sound sources (see Chapter 11) shall also be reported; b) a description of the noise type associated with the factory and any possible barrier effects at the microphone location; c) a description of the operating conditions associated with the factory during the measurement period; the date and time of the measurement; d) the climatic conditions during the measurement period, namely: 1) wind speed and direction; 3) relative humidity and air temperature;2) Processing, in which case their sound power levels should be determined in accordance with other appropriate standards. 12 Report Contents
The test report should state that the sound power levels used to evaluate the sound pressure levels in the environment were obtained in accordance with the requirements and methods of this standard. The report should include at least the following information:
a) The factory and its adjacent areas, with a diagram of the factory area, the measurement contour and the measurement positions on the measurement contour, including any background noise sources, reflective structures and objects that may affect the measured sound pressure level; the location of any separately measured sound source (see Chapter 11) should also be reported;
Describe the type of noise associated with the factory and any possible barrier effects at the microphone location; b)
Describe the operating conditions associated with the factory during the measurement period; the date and time of the measurement;
Climatic conditions during the measurement period, namely:
1) Wind speed and direction;
2) Relative humidity and air temperature;
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