05 VAC Impedance Tube Measurements
June 11, 2020Impedance Tube MeasurementsVibro-Acoustics Consortium Web MeetingUniversity of KentuckyVibro-Acoustics Consortium
Plane Waves in a PipeDaniel Russell, Penn State avesโintro/wavesโintro.htmlFor a pipe, the cutoff frequency is defined as:๐Vibro-Acoustics Consortium๐1.71๐2
Plane Waves in a PipeDaniel Russell, Penn State uperposition/superposition.htmlVibro-Acoustics Consortium3
Part 1 Measurement of Sound ImpedanceASTM E1050-95 (ISO 10534-2) Test MethodmicrophonesTransfer functionsampledriver (loudspeaker)Vibro-Acoustics Consortium4
Coordinate System and Microphone Locations๐ฅ๐ฅ๐ฅMaterial sampleSound sourceVibro-Acoustics Consortium5
Plane Wave TheoryTotal sound pressure at any point in the tube:๐ ๐ฅ๐ ๐๐ ๐-x traveling wave x traveling waveThe transfer function between points 1 and 2:๐ ๐ฅ๐ ๐ฅ๐ป๐ ๐๐๐ ๐๐ ๐๐ ๐๐ ๐๐๐๐ ๐๐ ๐is the pressure reflection coefficient of the materialVibro-Acoustics Consortium6
Solving for Material PropertiesSolving for ๐ :๐ ๐๐ป ๐๐ป ๐๐Normalized specific boundary impedance:๐ง๐๐11๐ ๐ Normal incident sound absorption๐ผVibro-Acoustics Consortium1๐ 7
Two-Microphone Standards1. ISO 10534-2, Acoustics-Determination of sound absorption coefficientand impedance in impedance tubes - Part 2: Transfer-function method2. ASTM E1050-10, Standard Test Method for Impedance andAbsorption of Acoustical Material Using a Tube, Two Microphones anda Digital Frequency Analysis SystemVibro-Acoustics Consortium8
Sound Absorption MeasurementSample holderwith rigid pistonVibro-Acoustics Consortium9
Cutting with Rotating BladeInexpensive and accurate if keptsharpenedStanley, Internoise 2012Vibro-Acoustics Consortium10
Stamping Press SystemUsed for low-density fibrousmaterialsVibro-Acoustics ConsortiumStanley, Internoise 201211
Water Jet CuttingExpensive butaccurateStanley, Internoise 2012Vibro-Acoustics Consortium12
โNot so Goodโ and โGoodโ SpecimensStanley, Internoise 2012Vibro-Acoustics Consortium13
Stanley, 2012 Specimen Preparation Face uniformly flush with cell lip Front surface even across lip of sample holder Extremely small (at most) and consistent gap betweenspecimen and sample holder No specimen compression in the holderVibro-Acoustics Consortium14
Variability of Melamine6 Samples of 1.91 cm MelamineAbsorption Coefficient10.80.60.40.200100020003000Frequency (Hz)Vibro-Acoustics Consortium1540005000
Variability Glass Fiber8 Samples of 5 cm Glass Fiber1Sound Absorption0.80.60.40.2001000Vibro-Acoustics Consortium20003000Frequency (Hz)1640005000
Effect of Cutter Size8 Samples of 1 inch thick 0.6 lbs/ftยณ MelamineAbsorption Coefficient10.80.60.41.375 inch Diameter cutter0.21.360 inch Diameter Cutter1.375 inch Diameter Cutter (with needles)001000Vibro-Acoustics Consortium20003000Frequency (Hz)1740005000
Effect of Adding Needles1.25 cm thick MelamineAbsorption Coefficient0.80.60.4Original3 needles6 needles12 needles20 needles25 needles0.200100020003000Frequency (Hz)Vibro-Acoustics Consortium1840005000
SummaryโWhile the use of an impedance tube system to measureacoustic absorption is not an extremely precise andrepeatable process due to unavoidable variations ofspecimen cutting and cell fit, the disciplined use of theguidelines stated in this paper will help to insure that testresults maintain a consistent level of accuracy and validity.The experience gained with repeated preparation andtesting will also contribute to a better feel for more subtleaspects of preparation and specimen fitting for testing.โStanley, Internoise 2012Vibro-Acoustics Consortium19
Part 2 Determination of Bulk Properties Determining the bulk properties Complex wave number and characteristic impedance Complex speed of sound and density Bulk properties are used For designing layered absorbers In FEM and BEM modelsVibro-Acoustics Consortium20
Porous Absorbers Property Determination๐ง๐๐ขL๐ and ๐ง๐๐๐๐๐ข๐ ๐โฒDetermination of Sound Absorption๐๐ข๐ง๐ ๐ผVibro-Acoustics Consortium๐งcos ๐ ๐ฟ๐/๐ง sin ๐ ๐ฟ๐๐ข๐ง๐ง๐๐๐๐1๐ ๐๐ง sin ๐ ๐ฟcos ๐ ๐ฟ๐๐ง cot ๐ ๐ฟ21๐๐ข
Porous Absorbers ๏ฟฝ๐๐๐๐๐ผ1๐ ๐๐๐ . ๐๐งIncident soundVibro-Acoustics Consortium22
Overview of ApproachesDirectMeasurement Two load method ASTM E 1050 Two cavity method Utsuno, 1989 Three microphone method Iwase et al., 1998Find bulk properties frommeasured flow resistivityWu, 1988; Mechel et al., 2002Measure FlowResistanceMeasure SoundAbsorptionCurve fit to find flow resistivitybased on empirical equationsSimรณn et al., 2006Find bulk properties frommeasured flow resistivityWu, 1988; Mechel et al., 2002Curve fit to find Biotparameters based on theoryFind bulk properties from fittedBiot parametersAllard, J. F., 1999Vibro-Acoustics Consortium23
Why Two-Loads?1 23 4๐ด๐ถ๐ต๐ท๐๐ขVibro-Acoustics Consortium๐๐๐๐24๐๐ขLoad ๐Load ๐
ASTM E2611-09Two-Load Method1 23 ๐ป,,๐๐ป, ๐2 sin ๐ ๐ ๐๐ป,๐2 sin ๐ ๐ Vibro-Acoustics Consortium๐ ๐For each load:Load ๐Load ๐๐๐ป๐ถ๐๐ท๐25๐,๐ป,2 sin ๐ ๐ ๐ป,๐๐ป, ๐2 sin ๐ ๐ ๐
ASTM E2611-09Transmission Loss MeasurementPressures and particle velocities at two ends of the sample:๐ด ๐ต๐ด ๐ต๐ข๐๐Four-pole matrix (subscripts ๐๐ ๐ข๐๐ ๐ข๐๐๐ข ๐ข๐ข๐ ๐ข๐๐๐๐๐ฟ20 logVibro-Acoustics ๐and ๐ indicate acoustic loads)๐ ๐๐ข๐ ๐๐ข๐ ๐ข๐ ๐ข๐ ๐ข๐ข๐ ๐ข๐ข๐ ๐ข๐ ๐ข1๐2๐๐๐26๐๐๐๐
ASTM E2611-09Two Loads1Load AAbsorption Coefficient0.80.60.4Load B0.2Load ALoad B0050010001500200025003000Frequency (Hz)Load A: Open tube.Load B: 10 cm sound absorbing material.Vibro-Acoustics Consortium27
ASTM E2611-09Two Load Method๐๐๐๐cos ๐ ๐๐ sin ๐ ๐๐งVibro-Acoustics Consortiumcos ๐ ๐๐๐๐ง๐ ๐๐๐ง sin ๐ ๐๐arctan๐๐ ๐ง28
Utsuno,1989Two Cavity MethodMicrophonesLoudspeaker๐ฟ๐PistonCavity 1Impedance tube๐ง๐ง๐ง1ln2๐๐๐ง๐ง๐ง ๐ง ๐ง๐ง๐ง๐ง๐ง๐ง๐๐ฟ๐Cavity 2๐ง๐ง ๐ง ๐ง๐ง๐งVibro-Acoustics Consortium29๐ง๐ง๐ง๐ง๐ง๐ง
Iwase et al., 1998Three Microphone MethodMicrophonesBLoudspeaker1Sample2Rigid EndA3sdLx 0Vibro-Acoustics Consortium30x
Iwase et al., 1998Three Microphone MethodReflection nes1Rigid end23Speaker๐ ๐ฟ๐๐ฅVibro-Acoustics Consortium310๐ฅ
Iwase et al., 1998Three Microphone MethodThe complex wave number of the sample is:๐1arccos๐1๐๐ ๐ ๐๐ปThe characteristic impedance of the sample is:๐งVibro-Acoustics Consortium1๐๐ง1๐ tan ๐ ๐๐ 32
2.5 cm Melamine Bulk Properties120Three Microphone (Re)Three Microphone (Im)Two Cavity (Re)Two Cavity (Im)Two Load (Re)Two Load (Im)42Complex Wave Number (1/m)Characteristic Impedamce60-280Three Microphone (Re)Three Microphone (Im)Two Cavity (Re)Two Cavity (Im)Two Load (Re)Two Load (Im)400-40-40100020003000Frequency (Hz)4000Vibro-Acoustics Consortium0500033100020003000Frequency (Hz)40005000
Melamine Sound Absorption Coefficient2.5 cm Melamine FoamAbsorption Coefficient10.80.60.4Two LoadTwo Cavity0.2Three Microphone00100020003000Frequency (Hz)Vibro-Acoustics Consortium3440005000
Melamine Transmission Loss2.5 cm Melamine Foam10Transmission Loss (dB)Two Load8Two CavityThree Microphone642001000Vibro-Acoustics Consortium20003000Frequency (Hz)3540005000
Overview of ApproachesDirectMeasurement Two load method ASTM E 1050 Two cavity method Utsuno, 1989 Three microphone method Iwase et.al., 1998Find bulk properties frommeasured flow resistivityWu, 1988; Mechel et al., 2002Measure FlowResistanceMeasure SoundAbsorptionCurve fit to find flow resistivitybased on empirical equationsSimรณn et al., 2006Find bulk properties frommeasured flow resistivityWu, 1988; Mechel et al., 2002Curve fit to find Biotparameters based on theoryFind bulk properties from fittedBiot parametersAllard, J. F., 1999Vibro-Acoustics Consortium36
Wu, 1988; Mechel et al., 2002Measure Flow ResistanceMeasureFlow Resistivity UsingASTM C522Sample(thickness ๐ก)ฮ๐Flow resistance:๐๐ขฮ๐๐ขPlug into Empirical ModelsSee Sound AbsorptiveMaterial WebinarFlow resistivity:Vacuum sourceVibro-Acoustics Consortiumฯ๐๐ก37
Overview of ApproachesDirectMeasurement Two load method ASTM E1050 Two cavity method Utsuno, 1989 Three microphone method Iwase et al., 1998Find bulk properties frommeasured flow resistivityWu, 1988; Mechel et al., 2002Measure FlowResistanceMeasure SoundAbsorptionCurve fit to find flow resistivitybased on empirical equationsSimรณn et al., 2006Find bulk properties frommeasured flow resistivityWu, 1988; Mechel et al., 2002Curve fit to find Biotparameters based on theoryFind bulk properties from fittedBiot parametersAllard, J. F., 1999Vibro-Acoustics Consortium38
Simon et al., 2006; Allard, J. F., 1999Curve Fitting MethodsMeasure soundabsorption coefficientMeasure soundabsorption coefficientMinimize least squareserror with respect toempirical equationsMinimize least squareserror with respect toanalytical equationsBiot ParametersFlow ResistivityPlug into empirical modelsPlug into theoretical modelWu (1988) or Mechel et al. (2002)Johnson-Champoux-Allard modelVibro-Acoustics Consortium39
2.5 cm Melamine Bulk Properties120Wu(Im) Flow Resistivity (Im)MeasuredWu(Re) Flow Resistivity (Re)MeasuredSimon(Re)LS CurveFit Flow Resistivity (Re)LS CurveSimon(Im)Fit Flow Resistivity (Im)LS Curve Fit Biot Parameters(Re)Johnson-Champoux-Allard(Re)LS Curve Fit Biot Parameters(Im)(Im)Johnson-Champoux-Allard42Complex Wave Number (1/m)Characteristic Impedance60-2Wu (Re) Flow Resistivity (Re)MeasuredWu (Im) Flow Resistivity (Im)MeasuredSimon(Re)LSCurveFit Flow Resistivity (Re)LSCurveFit Flow Resistivity (Im)Simon(Im)LSCurve Fit Biot tJCAParameters(Im)Johnson-Champoux-Allard (Im)9060300-30-60-40100020003000Frequency (Hz)MeasuredSimรณn Curve Fitting4000500012,100 Rayls/m11,400 Rayls/mVibro-Acoustics Consortium400100020003000Frequency (Hz)40005000
Summary Compared the various methods for determining thebulk properties of sound absorbers. Curve fitting approaches are adequate for commonsound absorbing materials.Vibro-Acoustics Consortium41
Part 3 Covers and Adhesives How do adhesives and covers between sound absorbing layers affectthe overall performance? How can we determine the acoustic properties of an adhesive or acover?Vibro-Acoustics Consortium42
Melamine Effect of Adhesives1.8 cm thick 9.6 kg/m3 Melamine FoamAbsorption Coefficient10.80.60.40.0 g0.3 g0.5 g0.7 g0.9 g0.20.2 g0.4 g0.6 g0.8 g1.0 g001000Vibro-Acoustics Consortium20003000Frequency (Hz)4340005000
Fiber Effect of Adhesives2.5 cm thick 19.2 kg/m3 FiberAbsorption Coefficient10.10.0101000Vibro-Acoustics Consortium0.0 g0.2 g0.3 g0.4 g0.5 g0.6 g0.7 g0.8 g0.9 g1.0 g20003000Frequency (Hz)4440005000
Transfer ImpedanceA transfer impedance is commonly used to model perforates, coversand source impedance. Particle velocity is assumed to be continuousacross the layer.๐๐ง๐๐ข๐ข๐ขp1 p2Vibro-Acoustics Consortium45๐ข
Wu, 2003Transfer Impedance MeasurementMeasurement of perforates or stics Consortium๐ง46๐๐ข๐ง
Transfer Impedance MeasurementMeasurement of adhesive layer or bonded ics Consortium๐ง47๐๐ข๐ง
Transfer Impedance Glue30.80.2 g (Re)0.3 g (Re)0.4 g (Re)0.5 g (Re)0.6 g (Re)0.7 g (Re)0.8 g (Re)0.9 g (Re)Transfer Impedance (Im)Transfer Impedance (Re)11.0 g (Re)0.60.40.200100020003000Frequency (Hz)4000Vibro-Acoustics Consortium5000480.2 g (Im)0.4 g (Im)0.6 g (Im)0.8 g (Im)1.0 g (Im)20.3 g (Im)0.5 g (Im)0.7 g (Im)0.9 g (Im)100100020003000Frequency (Hz)40005000
0.6 g of Glue Effect of Different Substrate5.0Transfer Impedance Im)Transfer Impedance e3.0Polyester2.01.00.00.00100020003000Frequency (Hz)4000Vibro-Acoustics Consortium5000490100020003000Frequency (Hz)40005000
Effect of CoversAbsorption Coefficient1.00.80.60.4Fiber with Cover0.2Fiber Only0.001000Vibro-Acoustics Consortium20003000Frequency (Hz)5040005000
Measurement Transfer ImpedanceTransfer y (Hz)4000Vibro-Acoustics Consortium500051๐งFoam๐ง๐งCover
Test Case 1Two Layers of Foam Bonded with AdhesiveGlue1 in2 inAbsorption Coefficient10.80.60.4Predicted using Transfer Impedance0.2Measured with GlueMeasured without Glue00Melamine FoamVibro-Acoustics Consortium52100020003000Frequency (Hz)40005000
Test Case 21CoverFiberAbsorption Coefficient0.80.60.4Transfer Matrix Method0.21.6 inMeasured with coverMeasured no cover00Vibro-Acoustics Consortium10005320003000Frequency (Hz)40005000
Test Case 3CoverTop CoverGlueFoamFoamGlueFiberFiber1 in1 inVibro-Acoustics Consortium54
Test Case 3Top Cover Foam LayerTop Cover Transfer Impedance154Absorption CoefficientTransfer ImpedanceTransfer Impedance (Re)Transfer Impedance (Im)3210.80.60.4Transfer Matrix Method0.2Measured000100020003000Frequency (Hz)4000Vibro-Acoustics Consortium5000550100020003000Frequency (Hz)40005000
Test Case 3Glue Fiber LayerGlue Transfer Impedance21Transfer Impedance (Im)1.5Absorption CoefficientTransfer ImpedanceTransfer Impedance (Re)10.50.80.60.4Transfer Matrix Method0.2Measured00100020003000Frequency (Hz)4000Vibro-Acoustics Consortium50005600100020003000Frequency (Hz)40005000
Test Case 3CoverGlueFoamGlass FiberAbsorption Coefficient10.80.60.4Measured0.2Transfer Matrix Method1 in1 inVibro-Acoustics Consortium005710002000Frequency (Hz)3000
Summary Transfer impedance is determined using an impedancedifference approach. Demonstrated capability to predict properties of layeredabsorbers.Vibro-Acoustics Consortium58
Transmission Loss StandardsASTM E2611-09, โStandard Test Method for Measurement of Normal IncidenceSound Transmission of Acoustical Materials Based on the Transfer MatrixMethod,โ American Society of Testing and Materials, Philadelphia, 2009.This standard Is designed to measure TL of โsoftโ barrier materials Is not specifically aimed at mufflers Only mentions the two-load method** Also one-load method for uniform materialsVibro-Acoustics Consortium59
Two-Load MethodMufflerLoudspeaker1324Load 1Open132Load 24AbsorbingmaterialTo and Doige, 1979Vibro-Acoustics Consortium60
Two-Source MethodConfiguration ALoudspeaker1324arbitraryZrImpedance tubeMufflerConfiguration B1324LoudspeakerZrMunjal and Doige, 1990Vibro-Acoustics Consortium61
ASTM E2611-09Transmission Loss Calculation 1 T12TL 20 log10 T11 cT21 T22 c 2 Transmission Loss (dB)10080Two-source methodTwo-load method6040200050010001500Frequency (Hz)Vibro-Acoustics Consortium62200025003000
Future Directions Develop a better method (or refine the approach) fordetermining the transmission loss of hard samples in animpedance tube. Explore best practices for cutting samples using the newwater jet cutter at the University of Kentucky.Vibro-Acoustics Consortium63
References ASTM E1050-19, โStandard Test Method for Impedance and Absorption of Acoustical MaterialsUsing a Tube, Two Microphones, and a Digital Frequency Analysis Systemโ, Philadelphia, 2019.ASTM C522-03, โStandard Test Method for Air Flow Resistance of Acoustical Materials,โPhiladelphia, 2003.ASTM E2611-19, โStandard Test Method for Measurement of Normal Incidence SoundTransmission of Acoustical Materials Based on the Transfer Matrix Method,โ Philadelphia, 2019.T. J. Cox and P. DโAntonio, Acoustic Absorbers and Diffusers: Theory, Design and Application,3rd Edition, CRC Press, Boca Raton, FL (2017).W. L. Li, X. Hua, and D. W. Herrin, โA Survey of Methods for Determining the Bulk Properties ofSound Absorbing Materials,โ Noise-Con 2014, Fort Lauderdale, FL, September 8-10 (2014).W. L. Li, D. W. Herrin, and J. Haylett, โMeasurement of the Transfer Impedance of Covers andAdhesives with Application to Multi-Layer Design,โ Noise-Con 2014, Fort Lauderdale, FL,September 8-10 (2014).Y. Salissou and R. Panneton, โWideband Characterization of the Complex Wave Number andCharacteristic Impedance of Sound Absorbers,โ Journal of the Acoustical Society of America,128(5), 2868-2876 (2010).T. W. Wu, C. Y. R. Cheng and Z. Tao, โBoundary Element Analysis of Packed Silencers withProtective Cloth and Embedded Thin Surfaces,โ Journal of Sound and Vibration, 261, 1-15 (2003).Vibro-Acoustics Consortium64
Measurement Measure Sound Absorption Measure Flow Resistance Two load method ASTM E 1050 Two cavity method Utsuno, 1989 . (Re) Two Cavity (Im) Two Load (Re) Two Load (Im) 33 . Two Load (Re) Two Load (Im) Vibro-Acoustics Consortium 34 Melamine Sound Absorption Coefficient 2.5 cm Melamine Foam 0 0.2 0.4 0.6 0.8 1 0 1000 2000 3000 4000 5000 .
Zero differential pressure type pilot operated 2 port diaphragm type 2.0 MPa (Resin body type 1.5 MPa) Aluminium, Resin, C37 (Brass), Stainless steel Note 1) NBR, FKM, EPDM Dust-tight, Water-jet-proof type (equivalent to IP65) Note 2) Location without corrosive or explosive gases 24 VAC, 48 VAC, 100 VAC, 110 VAC, 200 VAC, 220 VAC, 230 VAC, 240 VAC
2) Braced tube 3) Bundled tube 4) Tube-in-tube 5) Tubed mega frames A.Tube in Tube Structures The term "tube in tube" is largely self-explanatory in that second ring of columns, the ring surrounding the central service core of the building, are used as an ineer framed or braced tbe. The purpose of the second tube is to increase
frame tube, braced tube, bundled tube, tube in tube, and tube mega frame structures. The tube in tube structures and tube mega frame structures are the innovative and fresh concept in . These tubes are interconnected by system of floor slabs and grid beams.as the columns of outer and inner core tubes are placed so closely; it is not seen as a .
suring acoustic impedance and calibrating impedance heads and propose a general calibration technique for heads with multiple transducers. We consider the effect of transducer errors on impedance measurements and present a technique for distributing any measurement errors over the frequency range. To demonstrate the technique we use an impedance
* May be used with Mini Clik II, Toro Rainswitch model 850-74, or other normally closed Rainswitch devices. Models 2510 2520 2514 Power In 110 VAC 220 VAC 110 VAC Power Out 110 VAC 220 VAC 24 VAC Relay Contactor rated up to 2 H.P. Relay Contactor rated up to 2 H.P. Built in Transformer K-Rain - Hydrotek Controllers Instructions Page 9 of 9
0.5 A @ 230 Vac - Inrush Current max, 35 A @ 115 Vac 65 A @ 230 Vac 35 A @ 115 Vac 60 A @ 230 Vac Efficiency 79% typ. 88% typ. 80% typ. Leakage Current 1 mA @ 240 Vac Power Factor Correction Meets EN61000-3-2 Class A Output Nominal Voltage 5 V24 V - Tolerance /-2% Voltage Adjustable Range
1/16โ dia . (1 .6 mm) Maximum Temperature Limits (diaphragm / ball / seat . A- Solenoid 120 VAC,110 VAC and 60 VDC B- Solenoid 12 VDC, 24 VAC and 22 VAC C- Solenoid 240 VAC, 220 VAC and 120 VDC . y PX01X-HDS-XXX are Groundable Acetal pumps: Use the pump ground lug provided. Connect to a
2 A at 115 VAC - 230 VAC 4 A 6.3 A Half-cell, OmniRx, Omni TT 90 - 260 AR (Color Touch) 90 - 260 AR (auxiliary) 1.25 A at 115 VAC 0.75 A at 230 VAC 4 A 6.3 A Mobile supply cart 90 - 260 AR Medical grade 1.25 A at 115 VAC 0.75 A at 230 VAC 4 A 4 A Anesthesia Workstation, Anesthesia TT 90 - 260
