GB 10890-89
Methods of measuring and evaluating noise of pumps
This standard method for the determination of sound power level equivalent to the international standard ISO 3746-1979 "Acoustics - Noise source sound power level measurement - Overview method."
1, the main content and scope This standard specifies the pump noise measurement and evaluation methods.
This standard applies to submersible pumps, reciprocating pumps other than the various types of pumps and pumps with speed hydraulic coupling. In the application of this standard should be given priority to select the sound power level method, the conditions are not used only when the sound pressure level method. In case of dispute, the sound power level shall prevail.
2, the standard reference GB 3102.7 Acoustics and units GB 3240 commonly used in acoustic measurement frequency GB 3241 sound and vibration analysis with 1/1 and 1/3 octave GB 3768 noise source sound power level measurement Simplified GB 3785 sound level meter electrical, acoustical grade and test methods GB 3974 Acoustics terminology JJG 176 sound pressure level calibrator test procedures JJG 188 sound level meter test procedures JJG 277 standard sound source test procedures 3, the pump sound power level Determination methods The sound power level determined in this standard method is consistent with the method specified in GB 3768, the application of this method can more accurately understand the pump or pump noise level. When it is necessary to accurately determine the sound power level of the pump sound source, the influence of the noise of the prime mover (motor, internal combustion engine, etc.) should be taken into account. If necessary, measures should be taken to reduce the influence such as sound insulation cover of the prime mover.
3.1 Measurement Error Measurement error refers to the cumulative standard deviation caused by various factors.
According to this standard to measure the pump sound power level error is:
a. Pump sound source, the standard deviation of not more than 4dB;
b. The same standard pump in the same test environment, the standard deviation of not more than 3dB.
3.2 Acoustic measurement environment Ideal acoustic measurement environment should be in addition to a reflective surface (ground) no other reflective objects. Above the reflecting surface is approximately a free field. Suitable for this standard measurement environment for a wide range of outdoor or meet the requirements of the room. Measuring pump noise are generally in the laboratory (test pump).
3.2.1 Requirements for measuring environment (test room, test pump room) The standard for evaluating whether the laboratory meets the requirements is A / S ≧ 1 (A is the sound absorption in the laboratory room and S is the area of ​​the measuring surface) or the environment Correction value K2≤7.
3.2.2 Background noise requirements At the measuring point, the difference between the A level of the A level and the background level and the A level of the background level measured by the pump should be at least 3dB or more.
3.2.3 Wind speed outdoor measurement, the wind speed should be less than 6m / s and should use the hood.
Outdoor measurement, the motor cooling ventilation (feel) should use the hood.
3.3 Test Equipment 3.3.1 Overview Test equipment should be used in GB 3785 Type 2 or above sound level meter, and the accuracy of other test equipment. It is best to use extension cables or extension rods between the sound level meter or other test equipment and the microphone.
3.3.2 Calibration Before and after each measurement, the entire test system (including the cable) should be calibrated on one or more frequencies with a sound level calibrator with accuracy better than ± 0.5dB. Sound level calibrator shall JJG 176 procedures, sound level meter and other test equipment shall be regularly verified JJG 188 order to ensure the accuracy of test equipment.
3.4 Pump Installation and Operating Conditions 3.4.1 Installation The following points should be noted when installing the pump and test equipment:
a. In the laboratory measurement, the outlet throttle valve should be installed far away from the pump;
b. Inhalation and discharge piping noise is too large, should take measures to reduce the impact of noise;
c. Noise effects from other test equipment should be minimized.
3.4.2 Operating conditions In the measurement of centrifugal pumps, mixed flow pumps, axial flow vane pump noise, should be in the specified speed (± 5% tolerance), the provisions of the flow rate. In the measurement of gear pumps, vane pumps, screw pumps and other positive displacement pumps (Exhaust pump excluded) noise, the speed should be specified (± 5% tolerance), the provisions of the working pressure.
3.5 A Measurement of sound level 3.5.1 Measuring surface The microphone should be located on the imaginary measuring surface of the envelope sound source and one of two measuring surfaces may be used:
a. hemispherical measuring surface with radius r;
b. A rectangular parallelepiped measuring surface parallel to each side of the reference body.
When comparing the noise of the same type of pump, it is recommended to use the same measuring surface and the same measuring point position.
3.5.2 Reference Body The reference body is an envelope source and terminates in the smallest rectangular hexahedron on the reflecting surface. In determining the size of the reference body, the convex parts of the sound source (such as bosses, flanges, etc.) are not considered as long as the main radiator is not sonic energy. To be on the safe side, the benchmark may be chosen large enough to include dangerous work points.
When measuring pump noise, use a pump sound source to determine the reference volume.
In measuring pump unit noise, use the pump unit sound source (including pump and prime mover) to determine the reference body.
3.6 Hemisphere Measurement Surface Measurement When selecting the measurement surface, the hemisphere measurement surface should be selected with priority. For example, hemispherical measurement is required for single-stage, two-stage pumps, double suction pumps, medium pumps, gear pumps, vane pumps, surface.
3.6.1 Location of the measuring point Position the microphone on the surface of the imaginary hemisphere with radius r and area S = 2Ï€r2. The coordinates of the measuring points are shown in the left column of Table 1, the center of the hemisphere is the projection of the geometric center of the reference body on the reflecting surface, and the radius of the hemisphere is at least twice of the maximum size of the reference body.
If the sound source to be tested radiates an audible discrete frequency, selecting a measurement point above the ground level of 0.6r to determine A sound power level LWA will result in large errors. In this case, the measuring point can be located on the surface of the hemisphere just above the ground. However, it can be placed in such a way that the ground is hard (such as concrete or asphalt ground). The distance between the measuring points and the ground is not more than 0.05mm. The positions of these four measuring points are shown in the columns on the right of Table 1.
In addition to the required reflection of the ground, the microphone should not be less than 0.5mm away from other reflectors.
Table 1 Cartesian coordinates along the Cartesian coordinate system (0-X, Y, Z) at a distance from the center O of the hemisphere
The measuring point height is the measuring point on the reflecting surface of the measuring point of Z = 0.65r
X / r Y / r Z / r X / r Y / r Z / r
1 0.8 0.0 0.6 1.0 0.0
2 0.0 0.8 0.6 0.0 1.0
3 -0.8 0.0 0.6 -1.0 0.0 <0.5 m
4 0.0 -0.8 0.6 0.0 -1.0
3.6.2 test
The measuring position of the hemisphere relative to the measured sound source position (ie, the coordinates of X, Y) need to be determined by testing to determine that the sound level meter at a height of 0.6r along the Z axis is 0.8r A circular path to find the highest sound level A, so that the point coincides with one of the 4 measuring points.
Note: In general, the side lengths l1 and l2 of the reference body in Figure 1 are not necessarily parallel to the X and Y axes.
3.6.3 Measurement Measure the A sound level of the sound source on the 4 measuring points as shown in Figure 1. After the correction of the background noise (see 3.8 of this standard), calculate the average sound pressure level of the measuring surface according to 3.9 of this standard And average A sound power level.
3.7 Rectangular hexahedron measurement on the surface of the measurement Large multistage pumps, large vertical pump rectangular hexahedron measuring surface.
3.7.1 Location of the measuring point The microphone is located on the imaginary rectangular parallelepiped measuring surface whose envelope source is perpendicular to the surface of the reference body at a distance d. The main measuring point is shown in Fig. 2, the distance d is generally 1m, and the minimum distance should not Less than 0.25m, the height h of the measuring point from the reflecting surface is (H + d) / 2, H is the height of the reference body. Measuring point from the reflective surface minimum height of 0.15m. When the reference body height H is greater than 2.5m, the measuring points shall be arranged at two levels (H + d) / 2 and (H + d) in turn (see 3.7.3.3 of this standard) or according to the actual situation of the sound source , Then at each of the four measuring points at each altitude, the other two measuring points are:
a, the vertical distance from the top center of the datum body is d;
b. The highest sound level of A on the horizontal path specified in Subsection 3.7.2 of this standard (shown by the dotted line in Figure 2).
3.7.2 Test On the rectangular hexahedron measuring surface, the measuring point relative to the direction of the sound source is fixed. Through the test to determine the standard 3.7.1 b said the point, that is, using the sound level meter along the horizontal rectangular line shown in dashed line in Figure 2 to move to find the highest point A sound level.
Note: For safety reasons, the measuring point above the sound source may not be taken, but must be confirmed in the test to do so will not affect the sound power level accuracy.
3.7.3 Number of measuring points
3.7.3.1 Small sound source
The minimum number of measuring points for a small sound source is 6, that is, 4 basic measuring points plus a point above the sound source and the highest A sound level measured.
3.7.3.2 Loud source
For loud sources, the test shall be performed on the five basic measuring points as shown on the rectangular path in Figure 2 (except for the acoustically measured points above). If the measured sound level difference between the highest and lowest over 5dB, the need to add the following measuring points:
For horizontal scales t1 and t2, sound sources larger than 1.0 m need to add additional measuring points on the four corners of the horizontal path shown in FIG. 2.
For sound sources with a horizontal scale of more than 5.0m, in addition to increasing the measuring points at the four corners, additional intermediate measuring points as shown in Figure 2 shall be added. When the measuring distance d is less than or equal to 1 m, the measuring point spacing should be less than Equal to 2m; measuring point d is greater than 1m, the measuring point spacing should be less than or equal to 2d.
3.7.3.3 high sound source
For high sound sources (ie sound sources with a height of more than 2.5 m), measurements are required at two heights h1 = (H + d) / 2 and h2 = (H + d). Measured along the path from the highest A-level sound point should be included in the measuring point. At each height, the number of measuring points should be at least 5 points. When the height is h1, 5 basic measuring points are to be measured. When the height is h2, the measuring point on the four corners and the point with the highest sound level A are measured. A minimum of 11 points for high-sounding points, that is, 10 points on both levels plus a point on top.
3.7.4 Measurement
Measure the A sound level reading value LPAi of the sound source at the specified measuring point, and check the background noise of each measuring point according to Table 2 to obtain the LPAi-Kli value of A sound level at each measuring point, use the standard 3.9.1 Equation (1) calculates the average sound pressure level LPA for the measurement surface.
3.8 background noise correction
When measuring A sound level at each measuring point, if the difference between sound level A and background sound level A is less than 10 dB, the measured A sound level shall be corrected according to the correction amount listed in Table 2.
Table 2 background noise correction
When the sound source is working, the difference between the A sound level and the background sound level A shall be subtracted from the K1
3 3
4 2
5 2
6 & nb
7 1
8 1
9 0.5
10 0.5
> 10 0
3.9 Measurement surface average sound pressure level and A sound power level calculation
3.9.1 A Calculation of sound power level
A sound power level can be calculated by the following formula:
LWA = (LPA-K2) + 10lg (S / S0) (2)
Where: LWA - A sound power level, dB (reference value: IPW);
S - measuring surface and area, m2;
S0 - the reference area, lm2;
K2 - Environmental Correction Value, dB.
For hemispherical surfaces, S in Eq. (2) is given by:
S = 2Ï€r2
r - hemisphere radius, m.
For rectangular hexahedron measuring surfaces, S in Eq. (2) is calculated by:
S = 4 (ab + bc + ca)
Where: a = (L1 / 2) + d;
b = (L2 / 2) + d;
c = (L3 / 2) + d;
L1, L2, L3, - length, width, height, m ​​of the reference body;
d - measuring distance, referred to as ranging, m.
3.10 Determination of environmental correction value K2
3.10.1 Use a standard sound source to determine the K2 value
The standard sound source tested according to JJG 227 is placed in the test environment at the same location as the side sound source using the same measurement method as the sound source under test. Calculate the average sound pressure level of the standard sound source on the measuring surface according to the method in 3.9.1 of this standard (correction of background noise is required).
Calculate the sound power level Lw of the standard sound source in the environment of the sound source under test (pump) according to the formula (2) in 3.9.2 of this standard. At this time, K2 takes zero value.
For a standard sound source placed at multiple locations, the standard sound source sound power level Lw shall be calculated by averaging the average surface sound pressure level at which all the standard sound sources are placed.
Environmental correction value K2 can be obtained by the following formula:
K2 = Lw-Lwr (3)
Where: Lw-- sound power level of the standard sound source measured in the environment of the sound source under test (pump), dB;
Lwr - standard sound source calibration power level, dB.
The standard sound source placement method can be divided into alternative methods and juxtaposed two. When the sound source can be removed from the test site using the alternative method, the standard sound source placed in the same position with the sound source on the reflection plane, for smaller sound sources or larger but its length and width For sound sources smaller than 2, only one position is required. For loud sources with a ratio of length to width greater than 2, the standard sound source shall be placed in four positions, which are the four projections of the reference volume on the reflection plane Rectangular edge of the midpoint. When the measured sound source can not be removed from the test site using the parallel method, the standard sound source can be placed on the surface of the sound source or the measured sound source measured at four sides of the four locations on the measured sound source surface Should be a complete acoustic reflection surface, such as the measured sound source surface acoustic absorption coefficient is larger, the juxtaposition does not apply.
3.10.2 The amount of sound absorption A to determine the value of K2
Determination of the amount of sound absorption A, that is, measurement of the environment (laboratory, test pump sound) reverberation time T, refers to a sound T60 has reached a steady state, stop the sound source, the average sound density decay to 1 million from the original value (60dB) the required time, So measured reverberation time with broadband noise or impulse excitation, with A weighted receive.
The amount of sound absorption A is given by:
A = 0.16 (V / T) (4)
Where: V-- laboratory volume, m3;
T - laboratory reverberation time, s;
K2 is given by:
K2 = 10lg [1 + 4 / A / S] (5)
Where: S - measuring surface area (consistent with the measurement surface described in 3.5.1), m3.
4, pump sound pressure level measurement method
The method includes the determination of sound pressure level of A sound level and frequency band, the determination of sound pressure level of pump sound pressure band not necessary, and measurement only when deemed necessary.
4.1 on the measurement environment requirements
Measurement environment (laboratory or test pump) requirements should be as far as possible outside the ground reflection, that is, the distance from the sound pressure level attenuation value of not less than 5dB. Use one of the following methods to identify.
4.1.1 On the pump side (refer to figures 4 to 10 in the direction of measuring points P-1 to P-5), the difference between the sound level A measured at 1 m and 2 m of the pump body or between 0.5 m and 1 m from the pump body A measured sound level difference of not less than 5dB.
4.1.2 The standard sound source is installed in the test site where the pump is installed, the difference between the sound level A measured at 1m and 2m from the standard sound source or the sound level A measured at 0.5m and 1m away from the pump body is not less than 5dB.
4.1.3 If the requirements of 4.1.1 or 4.1.2 of this standard can not be met, the conditions of the measuring place (indoor size, equipment size, indoor layout of the pump) shall be marked separately and the standards 4.1.1 or 4.1.1 shall be specified. 2 times the measured distance from the sound pressure level attenuation value.
4.2 A sound level measurement method
4.2.1 measuring point position
A typical pump, prime mover (motor) measuring point selection as shown in Figure 4 ~ 10. The measuring points of other pumps can be determined with reference to this figure.
Measuring point high pump body surface horizontal distance of 1m.
The high points of the measuring points are as follows:
Pump axis distance from the acoustic reflector (ground) height of the center of the pump high, when the pump center is greater than 1m high, the measuring point high regulation 1m; when the pump center height greater than 1m, the measuring point height and center height the same.
4.2.2 Determination of A sound level and the average sound pressure level LPA calculation
Measure the sound source A sound level reading value LPAi at the measuring point, and check the background noise of each measuring point according to Table 2 to get the measured value of A sound level at each measuring point LPAi-Kli,
The average of the points measured around the pump when evaluating pump noise. In the assessment of unit noise, including the total average of all measuring points, are expressed with LPA.
4.3 band sound pressure level measurement method
4.3.1 The center frequency of 1/1 octave or 1/3 octave is given in Table 3.
Table 3 1/1 octave and 1/3 octave center frequency Hz
1/1 Octave Center Frequency 4000 8000
3150 6300
1/3 octave center frequency 4000 8000
5000 10000
4.3.2 Determination of band sound pressure level
The filter used should be consistent with the provisions of GB 3241. According to the need to choose 1/1 or 1/3 the octave band at the measuring point to measure the sound pressure level, the first by measuring the background noise band by sound pressure level. The measured pump noise sound pressure level than the same center frequency background noise level sound pressure level higher than 10dB, can not meet the above requirements, the difference of 3 ~ 10dB Table 2 were amended when the frequency band sound pressure level measured value.
5, the pump noise level evaluation method
In measuring the pump sound power level, with the evaluation of the surface sound pressure level to evaluate the pump noise level; in the measurement of pump A sound level, does not redefine the evaluation of the surface with the standard 4.2.2 of the average sound The pressure rating evaluates the noise level of the pump (where LPA is different from the average sound pressure level, LPA, of the measurement surface in the pump sound power level determination method).
5.1 Evaluation surface
When evaluating the noise level of a pump with its sound power level, a hemispherical surface of radius R is defined as the evaluation surface. ,
Where: l1, l2 - base length and width, m;
h - high with the pump center, m. The height of the horizontal pump center is the distance between the axis of the pump and the acoustic reflector (ground), m; the height of the vertical pump center is 1 / 2L, m. When the center is not greater than 1m high, h take 1m; when the center is higher than 1m, h center height.
5.2 Calculate the sound pressure level on the evaluation surface
Set the sound power level of the pump to be the sound pressure level on the evaluation surface of radius R with the following formula using the point source under the semi-free field condition:
LPA = LwA-20lg (R / Ro) -8.0 (7)
Where: LPA - sound pressure level on the evaluation surface with radius R, in dB;
LwA - pump sound power level, dB;
R - the radius of the specified evaluation surface, using equation (6), m;
Ro - base radius, 1m.
5.3 Divide the noise level limit of the pump
The three limits LA, LB, LC pump noise is divided into four levels A, B, C, D, D-level failure.
Use the following formula to determine the pump noise limit:
LA = 30 + 9.71g (Pun) (8)
LB = 36 + 9.71g (Pun) (9)
LC = 42 + 9.71g (Pun) (10)
Where: LA, LB, LC - Divided pump noise
Methods of measuring and evaluating noise of pumps
This standard method for the determination of sound power level equivalent to the international standard ISO 3746-1979 "Acoustics - Noise source sound power level measurement - Overview method."
1, the main content and scope This standard specifies the pump noise measurement and evaluation methods.
This standard applies to submersible pumps, reciprocating pumps other than the various types of pumps and pumps with speed hydraulic coupling. In the application of this standard should be given priority to select the sound power level method, the conditions are not used only when the sound pressure level method. In case of dispute, the sound power level shall prevail.
2, the standard reference GB 3102.7 Acoustics and units GB 3240 commonly used in acoustic measurement frequency GB 3241 sound and vibration analysis with 1/1 and 1/3 octave GB 3768 noise source sound power level measurement Simplified GB 3785 sound level meter electrical, acoustical grade and test methods GB 3974 Acoustics terminology JJG 176 sound pressure level calibrator test procedures JJG 188 sound level meter test procedures JJG 277 standard sound source test procedures 3, the pump sound power level Determination methods The sound power level determined in this standard method is consistent with the method specified in GB 3768, the application of this method can more accurately understand the pump or pump noise level. When it is necessary to accurately determine the sound power level of the pump sound source, the influence of the noise of the prime mover (motor, internal combustion engine, etc.) should be taken into account. If necessary, measures should be taken to reduce the influence such as sound insulation cover of the prime mover.
3.1 Measurement Error Measurement error refers to the cumulative standard deviation caused by various factors.
According to this standard to measure the pump sound power level error is:
a. Pump sound source, the standard deviation of not more than 4dB;
b. The same standard pump in the same test environment, the standard deviation of not more than 3dB.
3.2 Acoustic measurement environment Ideal acoustic measurement environment should be in addition to a reflective surface (ground) no other reflective objects. Above the reflecting surface is approximately a free field. Suitable for this standard measurement environment for a wide range of outdoor or meet the requirements of the room. Measuring pump noise are generally in the laboratory (test pump).
3.2.1 Requirements for measuring environment (test room, test pump room) The standard for evaluating whether the laboratory meets the requirements is A / S ≧ 1 (A is the sound absorption in the laboratory room and S is the area of ​​the measuring surface) or the environment Correction value K2≤7.
3.2.2 Background noise requirements At the measuring point, the difference between the A level of the A level and the background level and the A level of the background level measured by the pump should be at least 3dB or more.
3.2.3 Wind speed outdoor measurement, the wind speed should be less than 6m / s and should use the hood.
Outdoor measurement, the motor cooling ventilation (feel) should use the hood.
3.3 Test Equipment 3.3.1 Overview Test equipment should be used in GB 3785 Type 2 or above sound level meter, and the accuracy of other test equipment. It is best to use extension cables or extension rods between the sound level meter or other test equipment and the microphone.
3.3.2 Calibration Before and after each measurement, the entire test system (including the cable) should be calibrated on one or more frequencies with a sound level calibrator with accuracy better than ± 0.5dB. Sound level calibrator shall JJG 176 procedures, sound level meter and other test equipment shall be regularly verified JJG 188 order to ensure the accuracy of test equipment.
3.4 Pump Installation and Operating Conditions 3.4.1 Installation The following points should be noted when installing the pump and test equipment:
a. In the laboratory measurement, the outlet throttle valve should be installed far away from the pump;
b. Inhalation and discharge piping noise is too large, should take measures to reduce the impact of noise;
c. Noise effects from other test equipment should be minimized.
3.4.2 Operating conditions In the measurement of centrifugal pumps, mixed flow pumps, axial flow vane pump noise, should be in the specified speed (± 5% tolerance), the provisions of the flow rate. In the measurement of gear pumps, vane pumps, screw pumps and other positive displacement pumps (Exhaust pump excluded) noise, the speed should be specified (± 5% tolerance), the provisions of the working pressure.
3.5 A Measurement of sound level 3.5.1 Measuring surface The microphone should be located on the imaginary measuring surface of the envelope sound source and one of two measuring surfaces may be used:
a. hemispherical measuring surface with radius r;
b. A rectangular parallelepiped measuring surface parallel to each side of the reference body.
When comparing the noise of the same type of pump, it is recommended to use the same measuring surface and the same measuring point position.
3.5.2 Reference Body The reference body is an envelope source and terminates in the smallest rectangular hexahedron on the reflecting surface. In determining the size of the reference body, the convex parts of the sound source (such as bosses, flanges, etc.) are not considered as long as the main radiator is not sonic energy. To be on the safe side, the benchmark may be chosen large enough to include dangerous work points.
When measuring pump noise, use a pump sound source to determine the reference volume.
In measuring pump unit noise, use the pump unit sound source (including pump and prime mover) to determine the reference body.
3.6 Hemisphere Measurement Surface Measurement When selecting the measurement surface, the hemisphere measurement surface should be selected with priority. For example, hemispherical measurement is required for single-stage, two-stage pumps, double suction pumps, medium pumps, gear pumps, vane pumps, surface.
3.6.1 Location of the measuring point Position the microphone on the surface of the imaginary hemisphere with radius r and area S = 2Ï€r2. The coordinates of the measuring points are shown in the left column of Table 1, the center of the hemisphere is the projection of the geometric center of the reference body on the reflecting surface, and the radius of the hemisphere is at least twice of the maximum size of the reference body.
If the sound source to be tested radiates an audible discrete frequency, selecting a measurement point above the ground level of 0.6r to determine A sound power level LWA will result in large errors. In this case, the measuring point can be located on the surface of the hemisphere just above the ground. However, it can be placed in such a way that the ground is hard (such as concrete or asphalt ground). The distance between the measuring points and the ground is not more than 0.05mm. The positions of these four measuring points are shown in the columns on the right of Table 1.
In addition to the required reflection of the ground, the microphone should not be less than 0.5mm away from other reflectors.
Table 1 Cartesian coordinates along the Cartesian coordinate system (0-X, Y, Z) at a distance from the center O of the hemisphere
The measuring point height is the measuring point on the reflecting surface of the measuring point of Z = 0.65r
X / r Y / r Z / r X / r Y / r Z / r
1 0.8 0.0 0.6 1.0 0.0
2 0.0 0.8 0.6 0.0 1.0
3 -0.8 0.0 0.6 -1.0 0.0 <0.5 m
4 0.0 -0.8 0.6 0.0 -1.0
3.6.2 test
The measuring position of the hemisphere relative to the measured sound source position (ie, the coordinates of X, Y) need to be determined by testing to determine that the sound level meter at a height of 0.6r along the Z axis is 0.8r A circular path to find the highest sound level A, so that the point coincides with one of the 4 measuring points.
Note: In general, the side lengths l1 and l2 of the reference body in Figure 1 are not necessarily parallel to the X and Y axes.
3.6.3 Measurement Measure the A sound level of the sound source on the 4 measuring points as shown in Figure 1. After the correction of the background noise (see 3.8 of this standard), calculate the average sound pressure level of the measuring surface according to 3.9 of this standard And average A sound power level.
3.7 Rectangular hexahedron measurement on the surface of the measurement Large multistage pumps, large vertical pump rectangular hexahedron measuring surface.
3.7.1 Location of the measuring point The microphone is located on the imaginary rectangular parallelepiped measuring surface whose envelope source is perpendicular to the surface of the reference body at a distance d. The main measuring point is shown in Fig. 2, the distance d is generally 1m, and the minimum distance should not Less than 0.25m, the height h of the measuring point from the reflecting surface is (H + d) / 2, H is the height of the reference body. Measuring point from the reflective surface minimum height of 0.15m. When the reference body height H is greater than 2.5m, the measuring points shall be arranged at two levels (H + d) / 2 and (H + d) in turn (see 3.7.3.3 of this standard) or according to the actual situation of the sound source , Then at each of the four measuring points at each altitude, the other two measuring points are:
a, the vertical distance from the top center of the datum body is d;
b. The highest sound level of A on the horizontal path specified in Subsection 3.7.2 of this standard (shown by the dotted line in Figure 2).
3.7.2 Test On the rectangular hexahedron measuring surface, the measuring point relative to the direction of the sound source is fixed. Through the test to determine the standard 3.7.1 b said the point, that is, using the sound level meter along the horizontal rectangular line shown in dashed line in Figure 2 to move to find the highest point A sound level.
Note: For safety reasons, the measuring point above the sound source may not be taken, but must be confirmed in the test to do so will not affect the sound power level accuracy.
3.7.3 Number of measuring points
3.7.3.1 Small sound source
The minimum number of measuring points for a small sound source is 6, that is, 4 basic measuring points plus a point above the sound source and the highest A sound level measured.
3.7.3.2 Loud source
For loud sources, the test shall be performed on the five basic measuring points as shown on the rectangular path in Figure 2 (except for the acoustically measured points above). If the measured sound level difference between the highest and lowest over 5dB, the need to add the following measuring points:
For horizontal scales t1 and t2, sound sources larger than 1.0 m need to add additional measuring points on the four corners of the horizontal path shown in FIG. 2.
For sound sources with a horizontal scale of more than 5.0m, in addition to increasing the measuring points at the four corners, additional intermediate measuring points as shown in Figure 2 shall be added. When the measuring distance d is less than or equal to 1 m, the measuring point spacing should be less than Equal to 2m; measuring point d is greater than 1m, the measuring point spacing should be less than or equal to 2d.
3.7.3.3 high sound source
For high sound sources (ie sound sources with a height of more than 2.5 m), measurements are required at two heights h1 = (H + d) / 2 and h2 = (H + d). Measured along the path from the highest A-level sound point should be included in the measuring point. At each height, the number of measuring points should be at least 5 points. When the height is h1, 5 basic measuring points are to be measured. When the height is h2, the measuring point on the four corners and the point with the highest sound level A are measured. A minimum of 11 points for high-sounding points, that is, 10 points on both levels plus a point on top.
3.7.4 Measurement
Measure the A sound level reading value LPAi of the sound source at the specified measuring point, and check the background noise of each measuring point according to Table 2 to obtain the LPAi-Kli value of A sound level at each measuring point, use the standard 3.9.1 Equation (1) calculates the average sound pressure level LPA for the measurement surface.
3.8 background noise correction
When measuring A sound level at each measuring point, if the difference between sound level A and background sound level A is less than 10 dB, the measured A sound level shall be corrected according to the correction amount listed in Table 2.
Table 2 background noise correction
When the sound source is working, the difference between the A sound level and the background sound level A shall be subtracted from the K1
3 3
4 2
5 2
6 & nb
7 1
8 1
9 0.5
10 0.5
> 10 0
3.9 Measurement surface average sound pressure level and A sound power level calculation
3.9.1 A Calculation of sound power level
A sound power level can be calculated by the following formula:
LWA = (LPA-K2) + 10lg (S / S0) (2)
Where: LWA - A sound power level, dB (reference value: IPW);
S - measuring surface and area, m2;
S0 - the reference area, lm2;
K2 - Environmental Correction Value, dB.
For hemispherical surfaces, S in Eq. (2) is given by:
S = 2Ï€r2
r - hemisphere radius, m.
For rectangular hexahedron measuring surfaces, S in Eq. (2) is calculated by:
S = 4 (ab + bc + ca)
Where: a = (L1 / 2) + d;
b = (L2 / 2) + d;
c = (L3 / 2) + d;
L1, L2, L3, - length, width, height, m ​​of the reference body;
d - measuring distance, referred to as ranging, m.
3.10 Determination of environmental correction value K2
3.10.1 Use a standard sound source to determine the K2 value
The standard sound source tested according to JJG 227 is placed in the test environment at the same location as the side sound source using the same measurement method as the sound source under test. Calculate the average sound pressure level of the standard sound source on the measuring surface according to the method in 3.9.1 of this standard (correction of background noise is required).
Calculate the sound power level Lw of the standard sound source in the environment of the sound source under test (pump) according to the formula (2) in 3.9.2 of this standard. At this time, K2 takes zero value.
For a standard sound source placed at multiple locations, the standard sound source sound power level Lw shall be calculated by averaging the average surface sound pressure level at which all the standard sound sources are placed.
Environmental correction value K2 can be obtained by the following formula:
K2 = Lw-Lwr (3)
Where: Lw-- sound power level of the standard sound source measured in the environment of the sound source under test (pump), dB;
Lwr - standard sound source calibration power level, dB.
The standard sound source placement method can be divided into alternative methods and juxtaposed two. When the sound source can be removed from the test site using the alternative method, the standard sound source placed in the same position with the sound source on the reflection plane, for smaller sound sources or larger but its length and width For sound sources smaller than 2, only one position is required. For loud sources with a ratio of length to width greater than 2, the standard sound source shall be placed in four positions, which are the four projections of the reference volume on the reflection plane Rectangular edge of the midpoint. When the measured sound source can not be removed from the test site using the parallel method, the standard sound source can be placed on the surface of the sound source or the measured sound source measured at four sides of the four locations on the measured sound source surface Should be a complete acoustic reflection surface, such as the measured sound source surface acoustic absorption coefficient is larger, the juxtaposition does not apply.
3.10.2 The amount of sound absorption A to determine the value of K2
Determination of the amount of sound absorption A, that is, measurement of the environment (laboratory, test pump sound) reverberation time T, refers to a sound T60 has reached a steady state, stop the sound source, the average sound density decay to 1 million from the original value (60dB) the required time, So measured reverberation time with broadband noise or impulse excitation, with A weighted receive.
The amount of sound absorption A is given by:
A = 0.16 (V / T) (4)
Where: V-- laboratory volume, m3;
T - laboratory reverberation time, s;
K2 is given by:
K2 = 10lg [1 + 4 / A / S] (5)
Where: S - measuring surface area (consistent with the measurement surface described in 3.5.1), m3.
4, pump sound pressure level measurement method
The method includes the determination of sound pressure level of A sound level and frequency band, the determination of sound pressure level of pump sound pressure band not necessary, and measurement only when deemed necessary.
4.1 on the measurement environment requirements
Measurement environment (laboratory or test pump) requirements should be as far as possible outside the ground reflection, that is, the distance from the sound pressure level attenuation value of not less than 5dB. Use one of the following methods to identify.
4.1.1 On the pump side (refer to figures 4 to 10 in the direction of measuring points P-1 to P-5), the difference between the sound level A measured at 1 m and 2 m of the pump body or between 0.5 m and 1 m from the pump body A measured sound level difference of not less than 5dB.
4.1.2 The standard sound source is installed in the test site where the pump is installed, the difference between the sound level A measured at 1m and 2m from the standard sound source or the sound level A measured at 0.5m and 1m away from the pump body is not less than 5dB.
4.1.3 If the requirements of 4.1.1 or 4.1.2 of this standard can not be met, the conditions of the measuring place (indoor size, equipment size, indoor layout of the pump) shall be marked separately and the standards 4.1.1 or 4.1.1 shall be specified. 2 times the measured distance from the sound pressure level attenuation value.
4.2 A sound level measurement method
4.2.1 measuring point position
A typical pump, prime mover (motor) measuring point selection as shown in Figure 4 ~ 10. The measuring points of other pumps can be determined with reference to this figure.
Measuring point high pump body surface horizontal distance of 1m.
The high points of the measuring points are as follows:
Pump axis distance from the acoustic reflector (ground) height of the center of the pump high, when the pump center is greater than 1m high, the measuring point high regulation 1m; when the pump center height greater than 1m, the measuring point height and center height the same.
4.2.2 Determination of A sound level and the average sound pressure level LPA calculation
Measure the sound source A sound level reading value LPAi at the measuring point, and check the background noise of each measuring point according to Table 2 to get the measured value of A sound level at each measuring point LPAi-Kli,
The average of the points measured around the pump when evaluating pump noise. In the assessment of unit noise, including the total average of all measuring points, are expressed with LPA.
4.3 band sound pressure level measurement method
4.3.1 The center frequency of 1/1 octave or 1/3 octave is given in Table 3.
Table 3 1/1 octave and 1/3 octave center frequency Hz
1/1 Octave Center Frequency 4000 8000
3150 6300
1/3 octave center frequency 4000 8000
5000 10000
4.3.2 Determination of band sound pressure level
The filter used should be consistent with the provisions of GB 3241. According to the need to choose 1/1 or 1/3 the octave band at the measuring point to measure the sound pressure level, the first by measuring the background noise band by sound pressure level. The measured pump noise sound pressure level than the same center frequency background noise level sound pressure level higher than 10dB, can not meet the above requirements, the difference of 3 ~ 10dB Table 2 were amended when the frequency band sound pressure level measured value.
5, the pump noise level evaluation method
In measuring the pump sound power level, with the evaluation of the surface sound pressure level to evaluate the pump noise level; in the measurement of pump A sound level, does not redefine the evaluation of the surface with the standard 4.2.2 of the average sound The pressure rating evaluates the noise level of the pump (where LPA is different from the average sound pressure level, LPA, of the measurement surface in the pump sound power level determination method).
5.1 Evaluation surface
When evaluating the noise level of a pump with its sound power level, a hemispherical surface of radius R is defined as the evaluation surface. ,
Where: l1, l2 - base length and width, m;
h - high with the pump center, m. The height of the horizontal pump center is the distance between the axis of the pump and the acoustic reflector (ground), m; the height of the vertical pump center is 1 / 2L, m. When the center is not greater than 1m high, h take 1m; when the center is higher than 1m, h center height.
5.2 Calculate the sound pressure level on the evaluation surface
Set the sound power level of the pump to be the sound pressure level on the evaluation surface of radius R with the following formula using the point source under the semi-free field condition:
LPA = LwA-20lg (R / Ro) -8.0 (7)
Where: LPA - sound pressure level on the evaluation surface with radius R, in dB;
LwA - pump sound power level, dB;
R - the radius of the specified evaluation surface, using equation (6), m;
Ro - base radius, 1m.
5.3 Divide the noise level limit of the pump
The three limits LA, LB, LC pump noise is divided into four levels A, B, C, D, D-level failure.
Use the following formula to determine the pump noise limit:
LA = 30 + 9.71g (Pun) (8)
LB = 36 + 9.71g (Pun) (9)
LC = 42 + 9.71g (Pun) (10)
Where: LA, LB, LC - Divided pump noise
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