1、Designation: C 522 03Standard Test Method forAirflow Resistance of Acoustical Materials1This standard is issued under the fixed designation C 522; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number
2、in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the measurement of airflowresistance and the related measurements of specific airflowresistance and airflow resistivi
3、ty of porous materials that can beused for the absorption and attenuation of sound. Materialscover a range from thick boards or blankets to thin mats,fabrics, papers, and screens. When the material is anisotropic,provision is made for measurements along different axes of thespecimen.1.2 This test me
4、thod is designed for the measurement ofvalues of specific airflow resistance ranging from 100 to10 000 mks rayls (Pas/m) with linear airflow velocities rang-ing from 0.5 to 50 mm/s and pressure differences across thespecimen ranging from 0.1 to 250 Pa. The upper limit of thisrange of linear airflow
5、velocities is a point at which the airflowthrough most porous materials is in partial or completetransition from laminar to turbulent flow.1.3 A procedure for accrediting a laboratory for the pur-poses of this test method is given in Annex A1.1.4 This standard does not purport to address all of thes
6、afety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:C 384 Test Method for Impedanc
7、e and Absorption ofAcoustical Materials by the Impedance Tube Method2C 634 Terminology Relating to Environmental Acoustics2E 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of Test Methods33. Terminology3.1 Definitions: The definitions used in this test method areconta
8、ined in Terminology C 634.3.2 Definitions of Terms Specific to This Standard: Thefollowing items have been modified to exclude alternatingflow.3.2.1 airflow resistance, R; mks acoustic ohm(Pas/m3)the quotient of the air pressure difference across aspecimen divided by the volume velocity of airflow t
9、hrough thespecimen.3.2.2 airflow resistivity, r0; mks rayl/m (Pas/m2) of ahomogeneous material, the quotient of its specific airflowresistance divided by its thickness.3.2.3 lateral airflow resistivity of an anisotropic homoge-neous material, the airflow resistivity when the direction ofairflow is p
10、arallel to the face of the material from which the testspecimen is taken.3.2.4 specific airflow resistance, r; mks rayl (Pas/m)theproduct of the airflow resistance of a specimen and its area.This is equivalent to the air pressure difference across thespecimen divided by the linear velocity of airflo
11、w measuredoutside the specimen.3.2.5 transverse airflow resistivity of an anisotropic ho-mogeneous material, the airflow resistivity when the directionof airflow is perpendicular to the face of the material fromwhich the test specimen is taken.3.3 Application of Terms:3.3.1 The term airflow resistan
12、ce can be applied to speci-mens of any kind.3.3.2 The term specific airflow resistance has meaning onlywhen applied to a specimen of uniform thickness that ishomogeneous in directions parallel to its surface but notnecessarily homogeneous in the direction of airflow perpen-dicular to its surface.3.3
13、.3 The term airflow resistivity has meaning only whenapplied to a specimen that is homogeneous in directionsparallel to a and perpendicular to its surface but not necessarilyisotropic.3.4 Symbols:3.4.1 P = air pressure difference across test specimen, Pa.3.4.2 U = volume velocity of airflow through
14、the specimen,m3/s.3.4.3 u = U/S = linear velocity of airflow outside thespecimen, m/s.3.4.4 S = area of specimen, m.23.4.5 T = thickness of specimen, m.1This test method is under the jurisdiction of ASTM Committee E33 onEnvironmental Acoustics and is the direct responsibility of Subcommittee E33.01
15、onSound Absorption.Current edition approved Oct. 1, 2003. Published November 2003. Originallyapproved in 1963. Last previous edition approved in 1997 as C 522 87 (1997).2Annual Book of ASTM Standards, Vol 04.06.3Annual Book of ASTM Standards, Vol 14.02.1Copyright ASTM International, 100 Barr Harbor
16、Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4. Summary of Test Method4.1 This test method describes how to measure a steady flowof air through a test specimen, how to measure the air pressuredifference across the specimen, and how to measure thevolume velocity of airflow thro
17、ugh the specimen. From themeasurements may be calculated the airflow resistance, R, thespecific airflow resistance, r, and the airflow resistivity, r0.5. Significance and Use5.1 The specific airflow resistance of an acoustical materialis one of the properties that determine its sound-absorptive ands
18、ound-transmitting properties. Measurement of specific airflowresistance is useful during product development, for qualitycontrol during manufacture, and for specification purposes.5.2 Valid measurements are made only in the region oflaminar airflow where, aside from random measurement errors,the air
19、flow resistance (R = P/U) is constant. When the airflowis turbulent, the apparent airflow resistance increases with anincrease of volume velocity and the term “airflow resistance”does not apply.5.3 The specific airflow resistance measured by this testmethod may differ from the specific resistance me
20、asured by theimpedance tube method in Test Method C 384 for two reasons.In the presence of sound, the particle velocity inside a porousmaterial is alternating while in this test method, the velocity isconstant and in one direction only. Also, the particle velocityinside a porous material is not the
21、same as the linear velocitymeasured outside the specimen.6. Apparatus6.1 The apparatus, assembled as shown schematically inFig. 1, consists of the following components:6.1.1 Air Supply, a suction generator or positive air supplyarranged to draw or force air at a uniform rate through the testspecimen
22、.NOTE 1It may be necessary to use a large surge tank or other meansto reduce pressure fluctuations.6.1.2 Flowmeter, to measure the volume velocity of airflowthrough the specimen. It is preferable to have two or moreflowmeters with overlapping ranges to enable different airflowvelocities to be measur
23、ed to the same precision.6.1.3 Differential Pressure Measuring Device, for measur-ing the static pressure difference between the faces of thespecimen with respect to atmosphere.NOTE 2A slant manometer or pressure transducer system with a rangefrom 0 to 250 Pa is usually satisfactory, but a second in
24、strument with asmaller range, for example, 0 to 25 Pa, may be necessary for measuringsmall pressures to the desired precision.6.1.4 Specimen-Mounting Assembly, consists essentially ofa mounting plate and a specimen holder as shown in Fig. 2. Themounting plate has two holes for tube connections to th
25、epressure measuring device and to the airflow supply. Thespecimen holder, which is sealed to the mounting plate, ispreferably a transparent plastic tube at least 150 mm long witha diameter not less than 50 mm. For testing materials that willsupport themselves, such as disks cut from boards, a slight
26、FIG. 1 Schematic Diagram of Airflow ApparatusC522032taper at the top of holder will enable the specimen to be pressedinto position with a tight fit. For testing materials that will notsupport themselves, a removable screen held in position at least25 mm above the mounting plate may be used alone or
27、with aplunger assembly that can compress the specimen to a knownthickness. For testing thin materials, such as fabrics or papers,a flange at the top of the holder, together with a clamping ring,will enable the specimen to be held securely for testing.Specimens larger than the area of the holder can
28、be tested withsuitable fittings attached to the end of the holder. In such cases,care must be taken to ensure that the airflow through the edgesof the specimen is negligible in comparison to that through theface.NOTE 3If measurements are made concurrently by the impedancetube method, Test Method C 3
29、84, the two instruments may convenientlyhave the same inside diameter.7. Sampling7.1 Three or more specimens of a uniform sample materialshould be tested. When the sample is not uniform the speci-mens should be selected to include the variations in the properproportion, or several representative spe
30、cimens of the materialsshould be tested and the results averaged.8. Test Specimens8.1 BoardsRelatively hard, firm materials at least 5 mmthick. For transverse airflow resistance, disks are cut or sawedfrom the sample with diameter to fit tightly into the specimenholder. Coating the edges of the disk
31、s with grease may benecessary to form an airtight seal between the specimen and theholder wall. For lateral airflow resistance, several boards arelaminated together and a new board cut with faces at rightFIG. 2 Specimen HolderC522033angles to the original faces of the boards. Disks cut from thelamin
32、ated board are tested in the usual manner.8.2 BlanketsRelatively soft, flexible materials at least 5mm thick. Disks cut from the sample are laid on the removablescreen. If desired, the plunger assembly may be used tocompress the blanket to the desired thickness. Care must betaken to prevent leakage
33、around the edge of the specimen. Atransparent holder helps in spotting leaks.8.3 SheetsMaterials less than 5 mm thick. Disks withdiameter a little less than the outer diameter of the flange at thetop of the specimen holder are held in place with the clampingring with grease on the flange to limit th
34、e porous part of thespecimen to the inside diameter of the holder. Grease is alsoused to prevent flow of air into the edges of the specimen.Sheet materials with very low specific airflow resistance maybe tested by stacking layers of specimens separated with airspaces to obtain a measurable pressure
35、drop. The average resultfor a single layer should be reported.9. Procedure9.1 Mount the test specimen according to the type of test tobe made. Seal the specimen holder to the mounting plate andadjust the airflow to give readable settings on the flowmeterand pressure measuring device. Start at an air
36、flow velocity wellbelow 50 mm/s. Record the differential pressure, P, the flowrate, U, and the calculated quotient, R = P/U.9.2 Repeat the measurements several times, using a largerairflow rate each time. If the apparent resistance increases in asteady way, the airflow is probably turbulent and the
37、readingsmust be discarded. Make a series of at least three measure-ments at well separated airflow velocities (25 % recommendedminimum differential) below the turbulent level.9.3 Measurements should be made where possible within atemperature range of 22 6 5C. No adjustment to the calcu-lated results
38、 shall be made for barometric pressure.10. Calculation10.1 Calculated the airflow resistance in mks acoustic ohms(Pas/m3) from the expression:R 5 P/U (1)where P/U is the average value of ten or more readings madein the region of laminar airflow.10.2 Calculate the specific airflow resistance in mks r
39、ayls(Pas/m) from the expression:r 5 SP/U (2)10.3 Calculate the airflow resistivity in mks rayls/m (Pas/m2) from the expression:r05 SP/TU (3)10.4 See Table 1 to convert from cgs to mks and SI units.11. Report11.1 Report the following information:11.1.1 Complete identification and description of the m
40、ate-rial,11.1.2 Type of test and mounting,11.1.3 Description and dimensions of test specimen,11.1.4 Conditioning procedure used, if any,11.1.5 Number of specimens tested,11.1.6 Individual and average values of test results, in mksunits, and11.1.7 Temperature, barometric pressure, and relative hu-mid
41、ity.11.2 If a test is made intentionally in the transitional orturbulent airflow region, the reason should be given, and thelinear airflow velocities at which the measurements are madeshall be stated.12. Precision and Bias12.1 No quantitative statement on bias can be made at thistime since there is
42、presently no material available with knowntrue values of performance, which can be used for determiningthe bias of this test method.12.2 The within- and between-laboratory precision of thistest method, expressed in terms of the within-laboratory, 95 %Repeatability Interval, I(r), and the between-lab
43、oratory, 95 %,Reproducibility Interval, I(R), is listed in Table 2. Thesestatistics are based on the results of a round-robin test programinvolving seven laboratories.12.3 The significance of the Repeatability and Reproduc-ibility Intervals is as follows:12.3.1 Repeatability Interval, I(r)In the sam
44、e laboratoryon the same material, the absolute value of the difference intwo test results will be expected to exceed I(r) only about 5 %of the time.12.3.2 Reproducibility Interval, I(R)In different laborato-ries on the same material, the absolute value of the differencein two test results will be ex
45、pected to exceed I(R) only about5 % of the time.13. Keywords13.1 absorption; acoustical materials; airflow resistance;airflow resistivityTABLE 1 Conversion from cgs to mks and SI unitsTo convert from to Multiply bycgs acoustic ohm mks acoustic ohm (Pas/m3)105cgs rayl mks rayl (Pas/m) 10cgs rayl/cm m
46、ks rayl/m (Pas/m2)103cgs rayl/in. mks rayl/m (Pas/m2) 394mks rayl/in. mks rayl/m (Pas/m2) 39.4TABLE 2 Within-Laboratory Repeatability, I(r), and Between-Laboratory Reproducibility, I(R)MaterialAvg SpecificAirflowResistance(MKS Rayls)Repeat-abilityUncertainty(sr)Reproduc-ibilityUncertainty(sR)Repeat-
47、abilityIntervalI(r)Reproduc-ibilityIntervalI(R)Scotfelt foam 900.071 2.405 10.577 6.735 29.616C522034ANNEX(Mandatory Information)A1. LABORATORY ACCREDITATIONA1.1 ScopeA1.1.1 This annex describes procedures for accrediting atesting laboratory to perform tests in accordance with this testmethod. This
48、annex was prepared in accordance with GuideE 717 and describes procedures.A1.2 Referenced DocumentsA1.2.1 ASTM Standards:E 548 Guide for General Criteria Used for EvaluatingLaboratory Competence3E 717 Guide for Preparation of Accreditation Annex ofAcoustical Test Standards2A1.3 General RequirementsA
49、1.3.1 The testing agency shall make available to theaccrediting authority the information required by Sections 4 to7 of Practice E 548.A1.4 Requirements Specific to This Test MethodA1.4.1 ApparatusThe testing agency shall possess theapparatus described in:A1.4.1.1 Air SupplyA1.4.1.2 FlowmeterA1.4.1.3 Differential Pressure Measuring DeviceA1.4.1.4 Specimen-Mounting AssemblyA1.4.2 Calibration There are several types of flowmetersuitable for this test method. The testing agency shall providea valid calibration chart for the flowmeter, traceable to aNational In
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