Acoustics—Measurement of insertion loss of ducted silencers without flow—Laboratory survey method
Some standard content:
GB/T 16405—-1996
This standard specifies the measurement method of insertion loss of duct silencers in the absence of airflow. This standard is equivalent to ISO11691:1995 Acoustics—Measurement method of insertion loss of duct silencers in the absence of airflow—A simple laboratory method. This standard is usually applicable to silencers with a design flow rate not exceeding 15m/s. According to the specific conditions of my country, some articles of this international standard have been appropriately modified.
Appendix A is the appendix of this standard.
This standard will be implemented from December 1, 1996. This standard was proposed and managed by the National Technical Committee for Acoustic Standardization. The drafting unit of this standard is Beijing Institute of Labor Protection Science. The main drafters of this standard are: Ren Wentang, Li Xiaokuan, and Li Xiaoping. This standard is entrusted to the Noise Technical Committee of the National Technical Committee for Acoustic Standardization for interpretation. GB/T16405-—1996
ISO Foreword
ISO (International Organization for Standardization) is composed of standardization organizations from all over the world (ISO member countries). The main task of ISO technical committees is to draft international standards. Each member country interested in the standards drafted by the technical committee has the right to express its opinions to the committee. International organizations related to ISU (whether governmental or non-governmental) can participate in the formulation of standards. IS○ The International Electrotechnical Commission (IEC) has a close cooperative relationship in all electrical standards. The draft international standards adopted by the technical committee are submitted to the member countries for voting. At least 75% of the voting countries must agree to it before it can be published as a formal international standard.
International Standard ISO11691 was drafted by ISO/TC43 Acoustics Committee SC1 Noise Subcommittee. Appendix A of this standard is a suggestive appendix.
National Standard of the People's Republic of China
Measurement of Insertion Loss of Ducted Silencers without Flow-Laboratory Survey Method
AcousticsMeasurement of Insertion Loss of Ducted Silencers without Flow-Laboratory Survey Method1 Scope
1.1 General
This standard specifies the laboratory method for measuring the insertion loss of silencers without flow. GB/T16405—1996
eqv 1s0 11691:1995
This standard is mainly applicable to duct silencers such as resistive silencers with circular and rectangular cross-sections. The dimensions of the applicable silencers are: the diameter of the circular silencer and the two sides of the rectangular silencer are within the range of 80 to 2000 mm. The measurement method specified in this standard does not include airflow regeneration noise, so it is only applicable to silencers where airflow regeneration noise is not dominant. Due to different sound sources and the existence of pipeline flow field, the insertion loss value obtained by this measurement method may be different from the measurement results on site. Due to the transmission of structural vibration in the test pipeline, this measurement method has a maximum limit of insertion loss that can be measured. The determination method of the maximum limit and the corresponding correction method are shown in Appendix A.
1.2 Measurement uncertainty
The standard deviation of the reproducibility of this measurement method is shown in Table 1. Table 1 Standard deviation of reproducibility
1/3 octave band center frequency
50~1 250
1 600-~10 000
2 Referenced standards
Standard deviation of reproducibility
The following standards include provisions that constitute the provisions of this standard through reference in this standard. When the standard was published, the versions shown were valid. All standards will be revised. The parties using this standard should explore the possibility of using the latest version of the following standards. GB324182 1/1 and 1/3 octave filters for sound and vibration analysis (negIEC2251966) GB3785-83 Electrical and acoustic properties and measurement methods of sound level meters (neqIEC651:1979) GB6881-86 Determination of sound power level of acoustic noise sources by reverberation chamber precision method and engineering method (neqISO3741--1975, ISO 3742-1975, ISO 3743-1976) GB/T15193-94 Sound calibrator
GB/T4760--1995 Acoustic muffler measurement method (negIS07235:1991) GB/T3767-1996
Acoustics Determination of sound power level of noise sources by sound pressure by an engineering method similar to a white field above a reflecting surface (eqvIS0 GB/T 16404-1996 Acoustics - Determination of sound power level of noise sources by sound intensity method - Part 1: Measurement at discrete points National Technical Supervision Coal Screen 19.96-05-27 Approved 1996-12-01 Implementation GB/T 164051996 (IS0 9614. 1:1993) Measurement procedures for duct silencers - Insertion loss, airflow noise, pressure loss ISO72351991 Acoustics - 1 ISO3743-1:1994 Acoustics - Determination of sound power of noise sources - Engineering method for small and movable sound sources in a reverberant field Part 1: Comparison method for hard-walled test rooms IEC 6001- ... 804t1985 Integrating Sound Level Meter
3 Definitions
This standard adopts the following definitions.
3.1 Insertion loss
The reduction in the sound power level of the noise radiated from the pipe before and after the installation of the muffler, dB. 3.2 Test pipe tert durt
A straight standard pipe with a constant cross-sectional area located before and after the measuring muffler. 3-3 Substitute pipe snhstitutian duet A standard pipe with the same length as the measuring muffler and the same connecting cross-sectional area. If the inlet and outlet areas of the muffler are different, the substitute pipe should be made into a cone. If the inlet and outlet planes of the muffler are not parallel to each other, the substitute pipe should have a larger bending radius as much as possible to achieve a smooth transition.
3.4 Transition element transitionelement An element connecting the sound source pipe and the test pipe. Sometimes a transition element is also required between the test pipe and the muffler. 3.5 Standard pipe standardduet
Thin metal pipe, its thickness is usually: for small round pipes, it is 0.4~0.6mmtm, for large round pipes, it is 1.2~1.5mm, and for rectangular pipes, it is 0.8~1.0mm.
4 Test equipment
4.1 Test device
The test device is shown in Figure 1, which includes:
Noise measuring instrument (see 4.2)
Sound source equipment (see 4.3)
A transition element (see 4.4)
A test pipe (see 4.5)
Alternative pipe (see 4.5)
A test environment that meets the standard for determining the sound power level Speaker
4.2 Noise measuring instrument
Avoidance element
Test pipeline
GB/T16405—1996
Alternative pipeline
Test channel
Transition element
(depending on the need)
Unit: mm
Mixed room
The measurement system including microphone and cable shall comply with the provisions of GB3785 on type sound level meter. If an integrating sound level meter is used, it shall comply with the provisions of IEC 804. The filter shall comply with the relevant provisions of GB 3241. Before and after each series of measurements, a filter in accordance with IEC 942 shall be used. The measurement system is calibrated with the required Type I sound calibrator. 4.3 Sound source equipment
The sound source equipment shall be connected to the pipe in front of the test silencer, and it consists of a signal generator, an amplifier and a loudspeaker. The sound source consists of a loudspeaker with a diameter of 0.3m and a circular pipe with a diameter of 0.4m and a length of 1m with a sound field installed at the end: see Figure 2. The loudspeaker shall be placed in a sealed sound field box, and the back shall be filled with sound absorbing materials such as mineral wool. The loudspeaker group is connected to the test pipe through a pass element.
Sound absorbing material
Loudspeaker
Unit mtm
In the design and installation of the loudspeaker, attention shall be paid to avoiding the transmission of structure-borne sound, and minimizing the sound radiation of the box, and avoiding components
Note that the specific provisions of the size of this test device are mainly to reduce the reproducibility error of different test spaces. If the test requires the use of other smaller test equipment, it should be stated in the report.
4.4 Transition element
GB/T16405--1996
The transition element connecting the sound source and the test duct is an element with a sudden change in channel area. There is no limit on the ratio of the cross-sectional area of the sound source duct and the test duct.
If a transition element is used between the test duct and the muffler, its gradual transition length should not exceed 0.6m. 4.5 Test duct and alternative duct
The cross-sectional area of the test duct can be circular or rectangular, but its size should be as close as possible to the size of the inlet and outlet of the muffler. The ratio of the cross-sectional area of the test duct to the cross-sectional area of the muffler or the alternative duct should be within the range of 0.6 to 1.7. If necessary, a transition element can be used between the muffler and the duct. The same test duct should be used before and after the muffler, and its length is equal to 3.5m. If the insertion loss of the muffler is higher than the maximum limit that can be measured by the test device, the measures recommended in Appendix A should be taken to reduce the structure-borne sound and airborne sound radiation of the duct. 4.6 Test environment
If the method in GB6881 is used to measure the sound power level, the reverberation room shall comply with the relevant provisions of GB6881. The reverberation room that complies with the provisions of GB6881 is the preferred measurement environment. Other environments that meet the following standards are also allowed: - A free field above the reflecting surface that meets the requirements of GB/T3767: - A hard-walled room that meets the requirements of ISO3743-1 - Any environment that meets the requirements of GB/T 16404 5 Test procedure
The measurement shall be carried out in each 1/3 octave band within the frequency range of 50 to 10000 Hz. If the measurement environment does not meet the requirements in the entire frequency range mentioned above, the frequency that does not meet the requirements shall be clearly stated in the report. For the test slide and the alternative pipe, the sound source shall radiate the same sound power spectrum. If the terminal voltage of the speaker remains constant, this condition can usually be considered to be met.
If a reverberation chamber is used to measure the sound power level of the general outlet radiation, the traceability method and the average method of the spatial sound pressure level should comply with the requirements of IS 3741.
If other environments are used for measurement, spatial averaging should be performed in accordance with the requirements of the corresponding standards, and the measurement surface and microphone position plate should be determined according to the requirements for measuring the sound power level of the outlet radiation. If the spatial average sound pressure level of the alternative pipe radiation is LrI, and the spatial average sound pressure level of the installed muffler is LP2, the insertion loss of the muffler is:
D IplIrz
If the sound absorption of the reverberation chamber changes during the measurement, it should be corrected according to the method specified in GB6881. 1
When the report requires the frequency band insertion loss, if the following conditions are met and the sound pressure levels of each 1/3 octave band in the alternative pipe octave band are equal, the octave band insertion loss can be calculated using formula (2): D)n(dB)=-10lg(
(10-3/10+10-/10+10-/10)）
where D1, D2 and D, are the 1/3 octave band insertion losses in the octave band respectively. 6 Records
When conducting tests in accordance with this standard, the following records should be made: 6.1 Overview of test muffler
a) Type and application of muffler;
b) Transverse dimensions of the inlet and exhaust ports of the muffler; c) Length and weight of the muffler:
+++++++++++++( 2 )
GB/T16405—1996
e) Thickness, spacing and surface texture of the sound-absorbing sheets in the air flow channel (including perforation rate); f) Material, thickness, spacing, surface texture of the muffler sound-absorbing lining (including perforation rate); g) Other structural parameters of the muffler that may affect the test results. 6.2 Test environment overview
Standards for measuring sound power level, test environment, if GB 6881 standard is used to measure sound power level, only the volume of the reverberation chamber shall be recorded a)
b) If the reverberation chamber method is used to measure the sound power level, the position of the pipe exhaust port in the reverberation chamber shall be recorded. If other methods are used to measure the sound power level, the measurement position of the microphone shall be recorded: e) The connection type between the sound source and the test pipe; d) The thickness, material and structure of the test pipe
e) The grade and model of the measuring instrument.
6. 3 Acoustic measurement results
The frequency spectrum of the muffler insertion loss shall be given in a table, and it is best to give a spectrum diagram at the same time. The peek rate coordinates in the spectrum diagram shall be logarithmic coordinates.
7 Report
a) Date and time of measurement completion:
b) The report shall give at least the relevant information in 6.1), b), c) and 6.3. c) The report shall state the frequency ranges that meet the requirements of this standard and the frequencies that do not meet the requirements of this standard in the test results: d) If the filter chamber method is not used, the standard for obtaining the average sound pressure level or the sound intensity outside the transmission element shall be indicated. GB/T16405-1996
Appendix A
(Appendix to the standard)
Upper limit of insertion loss and corresponding correction method A1 Factors affecting the upper limit of insertion loss The factors affecting the upper limit of the insertion loss of a muffler test device include the solid-borne sound transmission of the test pipe, the airborne sound transmission through the test pipe and the walls of the test room, etc. The upper limit of the insertion loss of the test device can be controlled by improving the sound insulation of the test pipe, isolating the test pipe joints, and improving the sound insulation of the wall between the sound source and the receiving room. A2 The measurement method of the maximum limit of insertion loss is when the measuring silencer is not installed. Use high sound insulation materials (such as concrete, etc.) to seal the two ends of the test pipe, and measure its insertion loss according to the method specified in Chapter 5 of this standard, which is the maximum limit of insertion loss. A3 Correction method
The maximum limit of insertion loss of the silencer test device should be at least 10dB higher than the insertion loss measurement value of the test silencer in all frequency bands. If the difference is equal to 1~9dB, it is necessary to correct it according to Table A1. If the difference is less than 4dB, the measurement is invalid. Table A1 Insertion loss correction value
The difference between the maximum limit of insertion loss and the measured value of insertion loss of the test silencer. dE
The correction increase value of the auxiliary insertion loss of the test silencer一一 is for each 1/3 octave band in the octave band. 6 Records
When conducting tests according to this standard, the following records should be made: 6.1 Overview of test muffler
a) Type and application of muffler,
b) Transverse dimensions of the inlet and outlet of the muffler; c) Length and weight of the muffler:
+++++++++++++( 2 )
GB/T16405—1996
e) Thickness, spacing and surface structure of the sound absorbing sheet in the air flow channel (including perforation rate); f) Material, thickness, spacing, surface structure of the muffler sound absorbing lining sheet (including perforation rate); g) Other structural parameters of the muffler that may affect the test results. 6.2 Test environment overview
Standards for measuring sound power level, test environment, if GB 6881 standard is used to measure sound power level, only the volume of the reverberation chamber shall be recorded a)Www.bzxZ.net
b) If the reverberation chamber method is used to measure the sound power level, the position of the pipe exhaust port in the reverberation chamber shall be recorded. If other methods are used to measure the sound power level, the measurement position of the microphone shall be recorded: e) The connection type between the sound source and the test pipe; d) The thickness, material and structure of the test pipe
e) The grade and model of the measuring instrument.
6. 3 Acoustic measurement results
The frequency spectrum of the muffler insertion loss shall be given in a table, and it is best to give a spectrum diagram at the same time. The peek rate coordinates in the spectrum diagram shall be logarithmic coordinates.
7 Report
a) Date and time of measurement completion:
b) The report shall give at least the relevant information in 6.1), b), c) and 6.3. c) The report shall state the frequency ranges that meet the requirements of this standard and the frequencies that do not meet the requirements of this standard in the test results: d) If the filter chamber method is not used, the standard for obtaining the average sound pressure level or the sound intensity outside the transmission element shall be indicated. GB/T16405-1996
Appendix A
(Appendix to the standard)
Upper limit of insertion loss and corresponding correction method A1 Factors affecting the upper limit of insertion loss The factors affecting the upper limit of the insertion loss of a muffler test device include the solid-borne sound transmission of the test pipe, the airborne sound transmission through the test pipe and the walls of the test room, etc. The upper limit of the insertion loss of the test device can be controlled by improving the sound insulation of the test pipe, isolating the test pipe joints, and improving the sound insulation of the wall between the sound source and the receiving room. A2 The measurement method of the maximum limit of insertion loss is when the measuring silencer is not installed. Use high sound insulation materials (such as concrete, etc.) to seal the two ends of the test pipe, and measure its insertion loss according to the method specified in Chapter 5 of this standard, which is the maximum limit of insertion loss. A3 Correction method
The maximum limit of insertion loss of the silencer test device should be at least 10dB higher than the insertion loss measurement value of the test silencer in all frequency bands. If the difference is equal to 1~9dB, it is necessary to correct it according to Table A1. If the difference is less than 4dB, the measurement is invalid. Table A1 Insertion loss correction value
The difference between the maximum limit of insertion loss and the insertion loss measurement value of the test silencer. dE
The correction increase value of the auxiliary insertion loss of the test silencer一一 is for each 1/3 octave band in the octave band. 6 Records
When conducting tests according to this standard, the following records should be made: 6.1 Overview of test muffler
a) Type and application of muffler,
b) Transverse dimensions of the inlet and outlet of the muffler; c) Length and weight of the muffler:
+++++++++++++( 2 )
GB/T16405—1996
e) Thickness, spacing and surface structure of the sound absorbing sheet in the air flow channel (including perforation rate); f) Material, thickness, spacing, surface structure of the muffler sound absorbing lining sheet (including perforation rate); g) Other structural parameters of the muffler that may affect the test results. 6.2 Test environment overview
Standards for measuring sound power level, test environment, if GB 6881 standard is used to measure sound power level, only the volume of the reverberation chamber shall be recorded a)
b) If the reverberation chamber method is used to measure the sound power level, the position of the pipe exhaust port in the reverberation chamber shall be recorded. If other methods are used to measure the sound power level, the measurement position of the microphone shall be recorded: e) The connection type between the sound source and the test pipe; d) The thickness, material and structure of the test pipe
e) The grade and model of the measuring instrument.
6. 3 Acoustic measurement results
The frequency spectrum of the muffler insertion loss shall be given in a table, and it is best to give a spectrum diagram at the same time. The peek rate coordinates in the spectrum diagram shall be logarithmic coordinates.
7 Report
a) Date and time of measurement completion:
b) The report shall give at least the relevant information in 6.1), b), c) and 6.3. c) The report shall state the frequency ranges that meet the requirements of this standard and the frequencies that do not meet the requirements of this standard in the test results: d) If the filter chamber method is not used, the standard for obtaining the average sound pressure level or the sound intensity outside the transmission element shall be indicated. GB/T16405-1996
Appendix A
(Appendix to the standard)
Upper limit of insertion loss and corresponding correction method A1 Factors affecting the upper limit of insertion loss The factors affecting the upper limit of the insertion loss of a muffler test device include the solid-borne sound transmission of the test pipe, the airborne sound transmission through the test pipe and the walls of the test room, etc. The upper limit of the insertion loss of the test device can be controlled by improving the sound insulation of the test pipe, isolating the test pipe joints, and improving the sound insulation of the wall between the sound source and the receiving room. A2 The measurement method of the maximum limit of insertion loss is when the measuring silencer is not installed. Use high sound insulation materials (such as concrete, etc.) to seal the two ends of the test pipe, and measure its insertion loss according to the method specified in Chapter 5 of this standard, which is the maximum limit of insertion loss. A3 Correction method
The maximum limit of insertion loss of the silencer test device should be at least 10dB higher than the insertion loss measurement value of the test silencer in all frequency bands. If the difference is equal to 1~9dB, it is necessary to correct it according to Table A1. If the difference is less than 4dB, the measurement is invalid. Table A1 Insertion loss correction value
The difference between the maximum limit of insertion loss and the insertion loss measurement value of the test silencer. dE
The correction increase value of the auxiliary insertion loss of the test silencer
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