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GB/T 36079-2018 English PDF

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GB/T 36079-2018: Acoustics -- Procedures for determination of transmission loss, flow noise and total pressure loss coefficient for arrayed element dissipative silencers -- Equivalent measurement
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GB/T 36079-2018English839 Add to Cart 5 days [Need to translate] Acoustics -- Procedures for determination of transmission loss, flow noise and total pressure loss coefficient for arrayed element dissipative silencers -- Equivalent measurement Valid GB/T 36079-2018

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Basic data

Standard ID GB/T 36079-2018 (GB/T36079-2018)
Description (Translated English) Acoustics -- Procedures for determination of transmission loss, flow noise and total pressure loss coefficient for arrayed element dissipative silencers -- Equivalent measurement
Sector / Industry National Standard (Recommended)
Classification of Chinese Standard A59
Classification of International Standard 91.120.20
Word Count Estimation 42,470
Date of Issue 2018-03-15
Date of Implementation 2018-10-01
Issuing agency(ies) State Administration for Market Regulation, China National Standardization Administration

GB/T 36079-2018: Acoustics -- Procedures for determination of transmission loss, flow noise and total pressure loss coefficient for arrayed element dissipative silencers -- Equivalent measurement



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Acoustics--Procedures for determination of transmission loss, flow noise and total pressure loss coefficient for arrayed element dissipative silencers--Equivalent measurement ICS 91.120.20 A59 National Standards of People's Republic of China Acoustic unit side-by-side resistive muffler transmission loss, Airflow regenerative noise and determination of total pressure loss coefficient Equivalent method Published on.2018-03-15 2018-10-01 implementation General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China China National Standardization Administration issued

Content

Foreword III Introduction IV 1 Scope 1 2 Normative references 1 3 Terms and Definitions 1 4 symbol 4 5 Determination of the section and length of the measuring unit 5 6 Measurement methods and steps 6 7 Determination of sound transmission loss, airflow regeneration noise and total pressure loss of the muffler to be tested 7 8 Measurement uncertainty 9 9 Report content 9 Appendix A (Normative) Notes and illustrations of some terms 10 Appendix B (informative appendix) Method for determining the performance of a side-by-side muffler with a change in flow-through ratio 13 Appendix C (informative) Unit Side-by-side Muffler Measurement---Equivalent Method Example 20 Appendix D (informative) Unit-by-side muffler measurement of flow-through ratio change---Equivalent method example 27

Foreword

This standard was drafted in accordance with the rules given in GB/T 1.1-2009. This standard was proposed by the Chinese Academy of Sciences. This standard is under the jurisdiction of the National Acoustic Standardization Technical Committee (SAC/TC17). This standard was drafted. Shenzhen Zhongya Electromechanical Industry Co., Ltd., Northwestern Polytechnical University, Institute of Acoustics, Chinese Academy of Sciences, Tongji University, Nanjing University, Beijing Labor Protection Science Research Institute, Shanghai Jiaotong University, Changsha Aobang Environmental Protection Industry Co., Ltd., China Metrology Science Research Institute, Shanghai Academy of Environmental Sciences, China Academy of Building Research, Hefei University of Technology, Harbin Engineering University, Beijing University of Aeronautics and Astronautics. The main drafters of this standard. Fang Qingchuan, Chen Ke'an, Cheng Mingkun, Li Xiaodong, Lu Yadong, Mao Dongxing, Yu Wuzhou, Qiu Xiaojun, Zhang Bin, Li Xiaokuan, Jiang Weikang, Mo Jianyan, He Longbiao, Zhou Yude, Zhu Wenying, Tan Hua, Li Zhiyuan, Zhang Lin, Li Xiaodong, Xu Xin.

Introduction

When the geometry of the muffler to be tested is too large, the muffler acoustics cannot be performed on the conventional test bench according to GB/T 25516-2010. For the measurement of aerodynamic performance, a muffler with a smaller width and height is given in the normative appendix E of GB/T 25516-2010. The model is tested for requirements. This standard is based on the method given in Appendix E of GB/T 25516-2010. The selected criteria for the measurement of the model are specified in detail, and the measurement of the partial length of the longer muffler is given. The process of determining the acoustic performance and aerodynamic performance of the muffler, and obtaining the equivalent measurement result. This standard applies to not being able to press Sound transmission loss, airflow regenerative noise and total pressure loss of large unit side-by-side resistive muffler directly measured according to GB/T 25516-2010 Determination of the number. GB/T 25516-2010 Normative Appendix E, taking the chip muffler as an example, gives the muffler cross-section size beyond the test bench measurement An example and a brief description of dividing the side-by-side sound absorbing muffler into small modules on the section when the size is limited. This standard is for large and Examples of row-type resistive mufflers have been expanded and refined, including chip, array, honeycomb, etc., which clearly define these types of large and The exhaust muffler is used for the segmentation method and rules of the measurement unit for laboratory measurement. The division rules given in this standard, and GB/T The split example in Appendix E of 25516-2010 is consistent. According to GB/T 20431-2006, the full-pressure loss coefficient of the unit side-by-side resistive muffler defined in this standard can be decomposed into partial resistance. The force coefficient and the friction coefficient along the path, wherein the local resistance coefficient is independent of the length, and the friction coefficient along the path is proportional to the length. Voice Losses can be decomposed into discontinuous attenuation and propagation losses, where discontinuous attenuation is independent of length and propagation loss is proportional to length. In the laboratory Two unit side-by-side mufflers with identical section parameters but different lengths, through the local resistance coefficient and the frictional resistance along the path The number, discontinuous attenuation and propagation loss are measured separately, and the performance of the muffler to be tested whose actual length is greater than the length of the real test piece can be estimated. The parameters are obtained, and the equivalent measurement results of the sound transmission loss, the airflow regeneration noise, and the total pressure loss coefficient of the unit side-by-side muffler are obtained. Note. It is recommended that the length of the muffler to be tested is not more than three times the length of the real test piece. The larger the difference between the two lengths, the larger the error of the calculated result. Appendix A (Normative) of this standard illustrates some terms and definitions of this standard for easy understanding. Appendix B (informative) of this standard measures two sections according to the acoustic and aerodynamic principles of the unit side-by-side muffler. Sound transmission loss, airflow regeneration noise and total pressure loss of a side-by-side muffler with similar sound absorption sections (the same sound absorption section and similar net flow area) Number, the actual length and the arbitrary sound flow ratio of a unit side-by-side muffler, the sound transmission loss, airflow regeneration noise and The total pressure loss coefficient can provide theoretical basis and operation method for the design and acceptance of relevant noise control engineering projects. For the user's reference. Appendix C (informative appendix) of this standard gives a test for measuring large-scale unit side-by-side resistive muffler according to this standard. example. Appendix D (informative appendix) of this standard gives the performance of the unit side-by-side muffler with varying flow-through ratio according to the method of Appendix B. Definite example. The laboratory conditions, laboratory equipment and experimental procedures of this standard are the same as those of GB/T 25516-2010. Acoustic unit side-by-side resistive muffler transmission loss, Airflow regenerative noise and determination of total pressure loss coefficient Equivalent method

1 Scope

This standard specifies the method for determining the unit side-by-side resistive muffler measurement unit and the measurement list according to GB/T 25516-2010. The result of the measurement is derived, and the method of calculating the sound transmission loss, airflow regeneration noise and total pressure loss coefficient of the muffler to be tested is derived. measuring The laboratory measurement parameters of the unit include. ---The sound transmission loss in the presence of airflow and no airflow; --- Discontinuous attenuation with airflow and no airflow; --- Propagation loss in the presence of airflow and no airflow; ---Airflow regenerative noise sound power level; ---The total pressure loss when there is airflow; --- Total pressure loss coefficient; --- Partial pressure loss coefficient at the entrance and exit; --- Friction pressure loss coefficient; ---Inlet end form factor; ---Outlet end form factor; --- Sound absorption surface friction factor. This standard applies to all types of unit side-by-side resistive mufflers as defined in this standard, including in ventilation and air conditioning systems, Gas intake and exhaust gas exhaust systems and other similar systems, the muffler to be tested due to excessive geometry cannot be used in routine experiments Large muffler for room measurement. This standard applies to laboratory measurements under normal ambient temperature and atmospheric pressure conditions. Note. Unless otherwise stated, the muffler referred to in this standard is a resistive muffler.

2 Normative references

The following documents are indispensable for the application of this document. For dated references, only dated versions apply to this article. Pieces. For undated references, the latest edition (including all amendments) applies to this document. GB/T 20431-2006 Acoustic muffler noise control guide GB/T 25516-2010 Laboratory measurement methods for acoustic duct mufflers and air conditioning terminal devices, insertion loss, airflow regeneration Noise and total pressure loss

3 Terms and definitions

The following terms and definitions apply to this document. 3.1 Basic unit basicunit A minimum muffler module that is segmented from the large muffler and has the same size and shape. Note 1. With this module, the cross-sectional features of the large (size) muffler can be completely restored by side-by-side combination. Note 2. The typical basic unit sectional view is shown in Figure A.2 of Appendix A. 3.2 Unit side by side large resistive muffler largearrayedelementdissipativesilencer It consists of several resistive basic units arranged in parallel, and the overall size (section or length) is larger than that of conventional laboratory test equipment. To accept the scale of the muffler. Note. The sectional view of a typical unit side-by-side large-scale resistive muffler is shown in Figure A.1 of Appendix A. 3.3 Silencer silencertobemeasured Complete unit provided by the manufacturer/supplier for the measurement of acoustic loss, airflow regenerative noise and total pressure loss factor Side-by-side large muffler. 3.4 Measuring unit measurementunit The basic units consist of m × n (n, m is the number of rows and columns ≥ 1), and the cross-sectional dimensions are matched with the laboratory test device for acoustics. Muffler module for performance and aerodynamic performance measurements. Note. The section of a typical measuring unit is shown in Figure A.3 of Appendix A. 3.5 Sound absorber dissipativeabsorber The key acoustic components that make up the unit side-by-side muffler. In addition to the shroud at both ends, the cross-sectional shape and dimensions of the middle part are always guaranteed. Consistently, the internal filling material is porous material (such as mineral wool, glass wool, open-cell foamed plastic, etc.), and the surface acoustic impedance is the same everywhere. Note. The sound absorber structure is shown in Figure A.4 and Figure A.5 of Appendix A. 3.6 Same model sound absorber sametypeofthedissipativeabsorber In addition to the effective length, the windward end shroud, the outlet end shroud, the cross-sectional shape and size are the same, and the internal structure and material of the sound absorption section are finished. All the same sound absorbers. 3.7 Effective noise reduction length The length of the sound absorption section of the sound absorbing body in the muffler is usually equal to the total length of the sound absorbing body along the airflow direction minus the hood of both ends length. Note. The unit of effective noise reduction length is meters (m). 3.8 Throughflow ratio ratioofflowareatofacearea/cross-sectionarea The ratio of the net flow cross-sectional area of the muffler (or unit) to the total area of the section. 3.9 Transmission loss transmissionloss Dt The difference between the sound power level at the inlet end of the muffler and the sound power level at the exit end of the muffler. Note 1. In this standard, the sound transmission loss is decomposed into two parts. discontinuous attenuation and propagation loss. Note 2. The unit of sound transmission loss is decibel (dB). 3.10 Discontinuous attenuation discontinueyattenuation Ds The amount of change in sound power level caused by a change in the cross-section of the muffler at the inlet and outlet ends. Note. The unit of discontinuous attenuation is decibel (dB). 3.11 Unit length propagation loss propagationlosspermeter Da Sound power level per unit length formed by uniform acoustic propagation attenuation in the middle section of a muffler with a fixed cross section and a uniform longitudinal structure The amount of attenuation, expressed in decibels per meter (dB/m). Given the effective muffling length l the acoustic propagation loss of the muffler is defined as DA = Da · l. The sound transmission loss of the unit side-by-side muffler consists of two parts, discontinuous attenuation and propagation loss, expressed by equation (1). Dt=Ds DA (1) In the formula. Ds---discontinuous attenuation of the muffler in decibels (dB); DA---The sound propagation loss of the muffler in decibels (dB). 3.12 Headwind speed facevelocity Vf The wind speed at the inlet section of the muffler airflow is related to the volume flow into the muffler and the cross-sectional area at the muffler inlet. Equation (2). Vf= Qv (2) In the formula. Qv---volume flow into the muffler in cubic meters per second (m3/s); S --- The cross-sectional area at the entrance of the muffler, also known as the windward area, in square meters (m2). Note. The unit of oncoming wind speed is meters per second (m/s). 3.13 Total pressure loss totalpressurelossofthesilencer Δp The total differential pressure between the upstream and downstream of the muffler. Note. The unit of total pressure loss is Pascal (Pa). 3.14 Local pressure loss coefficient localpressurelosscoefficientrelatedtooutletandinlet Ξs The sum of the partial total pressure loss of the airflow outlet and the local total pressure loss of the airflow inlet and the upstream oncoming dynamic pressure (dynamic pressure based on the surface wind speed) ratio. It is related to the aerodynamic shape of the inlet and outlet ends and the flow ratio of the muffler, see equation (3). Ξs= Sb Sf · 0.5·ξ1· Sf Sb ÷ ξ2 Êê Úú (3) In the formula. Sb---The blocking area of the muffler section, in square meters (m2); Sf---the flow area of the muffler section, in square meters (m2); Ξ1---Inlet end form factor, dimensionless; see Appendix A Figure A.7 Gradual reduction; Ξ2---Outlet end form factor, dimensionless; see Appendix A Figure A.7 Gradient expansion. 3.15 Frictional pressure loss coefficient frictionpressurelosscoefficient Ξf The ratio of the frictional pressure loss along the upstream to the upstream oncoming dynamic pressure. Surface roughness characteristics, blocking area, and flow area of the sound absorbing body (sheet) Off, proportional to the wet week and length, see equation (4). Ξf= 4ξ3 Sf Sb Sf l=ξl·l (4) In the formula. U --- Wet circumference of the muffler section (sound absorption circumference), the unit is meters (m); Sf---the net flow area of the muffler, in square meters (m2); Sb---The blocking area of the muffler section, in square meters (m2); l --- The effective noise reduction length of the muffler, in meters (m); Ξ3---The surface friction coefficient of the sound absorber is related to the surface roughness, dimensionless; Ξl---The coefficient of friction pressure loss per unit length, in units per meter (m-1). 3.16 Total pressure loss coefficient totalpressurelosscoefficient The ratio of the total pressure loss of the muffler to the upstream dynamic pressure of the muffler, see equation (5). ξ= Δp 2ρv (5) In the formula. Δp---total pressure loss in Pascal (Pa); ρ --- muffler upstream air density in kilograms per cubic meter (kg/m3); Vf --- Oncoming wind speed in meters per second (m/s) (see 3.12). Note. Some data have different definitions of the total pressure loss coefficient as given in GB/T 25516-2010. Therefore, the total pressure loss system used in other literatures When you count a number, you need to check its definition. For example, some definitions replace vf with the velocity of the airflow at the narrowest cross section of the muffler, which leads to this definition. The total pressure loss coefficient ξ value is lower than the value defined in this standard. The total pressure loss consists of the local pressure loss (local resistance) at the inlet and outlet and the frictional pressure loss (frictional resistance) along the path. Therefore, the total pressure loss The relationship between the coefficient of loss ξ and the local pressure loss coefficient ξs of the inlet and outlet (see 3.14) and the frictional pressure loss coefficient ξf (see 3.15) can be used. Expressed by the formula (6). ξ=ξs ξf=ξs ξl·l (6) 3.17 Airflow regenerative noise flownoise, regeneratedsound The noise generated when the airflow passes through the muffler. Note 1. Some literature is called airflow noise or regenerative noise; Note 2. See GB/T 20431-2006, 3.18 and GB/T 25516-2010, 3.14 for details. 3.18 Test frequency range frequencyrangeofinterest The center frequency is 1/3 times the frequency band of 100 Hz to 5000 Hz. Note. In practical applications, the frequency range is generally a octave band with a center frequency of 125 Hz to 4000 Hz. In some applications, the measured frequency range can be extended 1/3 times the frequency band from the center frequency of 50 Hz to 10000 Hz (the center frequency of the octave band is 63 Hz to 8000 Hz).

4 symbol

Table 1 lists the symbols referenced in this standard and their meanings. Table 1 symbol Symbol term unit comment Di insertion loss dB Dt transmission loss dB Ds discontinuous attenuation dB Da propagation loss dB LW airflow noise sound power level dB LW, J dB sound power level of the measuring unit at an oncoming wind speed of 1 m/s LW, B dB and muffler structural characteristics and frequency related values, see B.5 K - the relationship between the airflow noise and the flow rate F - See Appendix B, B.5 (B.7) Z - See Appendix B, Form B.6 (B.11) Δp total pressure loss Pa 消 Muffler full pressure loss coefficient - Ξs partial pressure loss coefficient - Ξf friction pressure loss coefficient - Ξl friction loss coefficient per unit length 1/m Ξ1 Entrance end form factor - see Appendix A for sudden reduction and gradual reduction Ξ2 Outlet end form factor - see Appendix A for sudden expansion and gradual expansion Ξ3 Sound Absorption Surface Friction Factor - Sb cross section blocking area m2 Sf cross-sectional flow area, channel net flow cross-sectional area m2 S Windward area, total area of section m2 S=sb sf Vf headwind speed m/s l muffler effective length m L muffler profile length m U muffler section sound absorption perimeter m R The ratio of the net flow area to the total area of the section - R = sf/S = sf/(sb sf)

5 Determination of the section and length of the measuring unit

The number of basic unit rows and columns constituting the measuring unit is determined according to the basic unit of the muffler to be measured. Priority can be measured in the laboratory The maximum number of rows and columns of the quantity constitutes the measurement unit. The measurement unit is preferably composed of the maximum number of rows and columns that can be measured in the laboratory. Appendix A Figure A.7 shows an illustration of a typical measurement unit section. It should be determined that the cross-sectional configuration and the end form are exactly the same two measuring units of length l1 and l2, respectively identified as measuring units A and measuring unit B, the effective length thereof satisfies l1≥900mm; l2≥1.5l1. The selection of l2 requires prediction of the acoustic loss of the measuring unit of length l2, requiring measurement devices within the measurement frequency (or frequency band) The ultimate insertion loss is at least 10 dB greater than the acoustic loss of the measuring unit. Note 1. Refer to Appendix C of GB/T 25516-2010 for the definition and measurement method of the limit insertion loss of the measuring device. Note 2. See Appendix C for examples of measurement unit determination. Note 3. Refer to Appendix B for the method of determining the measurement unit for the change of the flow ratio. Note 4. See Appendix D for examples of the determination of the measurement unit for the change in the flow ratio.

6 Measurement methods and steps

6.1 For each frequency band within the test frequency range, measure a variety of oncoming wind speeds according to GB/T 25516-2010 (typically, selectable Dynamic insertion loss of measurement unit A and measurement unit B determined in Chapter 5 under vf≈0, 2, 4, 6, 8, 10, 12, 14 m/s), and Table 2 is obtained. Multiple sets of data listed in . Table 2 Insertion loss of measuring unit at different wind speeds Headwind speed avf/m·s-1 0 2 4 6 8 10 12 Measuring unit A (l=l1) Di,A,0 Di,A,2 Di,A,4 Di,A,6 Di,A,8 Di,A,10 Di,A,12 Measuring unit B(l=l2) Di,B,0 Di,B,2 Di,B,4 Di,B,6 Di,B,8 Di,B,10 Di,B,12 Note 1. Each grid of data is the insertion loss of the corresponding test band. Note 2. When the difference between the measurement data and the limit insertion loss of the measurement system is less than 10 dB, it needs to be recorded as “≥”. Note 3. The forward airflow (the direction of sound wave propagation in the same direction as the airflow) and the reverse airflow (the direction of sound wave propagation are opposite to the airflow) need to be measured separately. Note 4. The subscripts of the insertion loss in the table are identified as the measuring unit and the oncoming wind speed. a Based on actual measurements. 6.2 For each frequency band within the measurement frequency range, measure a variety of oncoming wind speeds according to GB/T 25516-2010 (typically, select vf The airflow regeneration noise of measurement unit A and measurement unit B determined in Chapter 5 under ≈2, 4, 6, 8, 10, 12, 14m/s) is obtained in Table 3. Multiple sets of data for the column. Table 3 Measurement unit airflow regenerative noise sound power level at different wind speeds Headwind speed avf/m·s-1 2 4 6 8 10 12 14 Measuring unit A (l=l1) LW, A, 2 LW, A, 4 LW, A, 6 LW, A, 8 LW, A, 10 LW, A, 12 LW, A, 14 Measuring unit B (l=l2) LW, B, 2 LW, B, 4 LW, B, 6 LW, B, 8 LW, B, 10 LW, B, 12 LW, B, 14 Note 1. Each grid of data is the airflow noise sound power level of the corresponding test band. Note 2. When the difference between the measured data and the background noise data is less than 10 dB, it needs to be recorded as “≤”. Note 3. The upstream airflow noise and the downstream airflow noise must be measured separately. Note 4. The subscripts of the sound power level of the airflow noise in the table are identified as the measuring unit and the oncoming wind speed. a Based on actual measurements. 6.3 According to GB/T 25516-2010, measure a variety of oncoming wind speeds (typically, select vf≈2, 4, 6, 8, 10, 12, 14m/s) The total pressure loss of measurement unit A and measurement unit B determined in Chapter 5, the multiple sets of data listed in Table 4 were obtained. Table 4 Total pressure loss of measuring unit at different wind speeds Headwind speed avf/m·s-1 2 4 6 8 10 12 14 Measuring unit A (l=l1) ΔpA,2 ΔpA,4 ΔpA,6 ΔpA,8 ΔpA,10 ΔpA,12 ΔpA,14 Measurement unit B (l=l2) ΔpB,2 ΔpB,4 ΔpB,6 ΔpB,8 ΔpB,10 ΔpB,12 ΔpB,14 Note. The subscripts of the total pressure loss in the table are identified as the measuring unit and the oncoming wind speed. a Based on actual measurements. 6.4 Obtain the total pressure loss coefficient of measurement unit A and unit B according to the data in Table 4 and equation (6) (see Table 5). Table 5 Total pressure loss coefficient of measuring unit at different wind speeds Headwind speed vf/m·s-1 2 4 6 8 10 12 14 Measuring unit A (l=l1) ξA,2 ξA,4 ξA,6 ξA,8 ξA,10 ξA,12 ξA,14 Measuring unit B (l=l2) ξB,2 ξB,4 ξB,6 ξB,8 ξB,10 ξB,12 ξB,14 Note. The total pressure loss factor is converted according to the exact value of the oncoming wind speed recorded during the measurement. And ξB. Note. See Appendix C for examples of measurement of ins...

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