customers material characteristics

1Areva Strategic Assessment Review 2007-2011 1

Materials for Vibro-Acoustic applications

01dB-SCS solutionsGianni Amadasi


Materials main groupsFluidsIsotropic solid (Structure Materials elastic with same properties in all directions):

steel, glass, etc.Orthotropic solid (Structure Materials elastic with different properties vs. directions):

compositeParameters: Density, Youngs Modulus, Poissons ratio, Damping Loss factor

Mass materials (un-elastic):

septum, rubbers, EPDM, etc.Density, Insertion Loss, Transmission Loss

Spring like Materials:

Felts, FoamAcoustic Absorption and Impedance, Porosity, Flow Resistance, Tortuosity, Complex Modulus, Bulk Loss Factor

Damping Materials (un-elastic):

septum, rubbers, EPDM, etc. Parameters: Density, Youngs Modulus, Poissons ratio, Damping Loss factor

Key Words:

Noise control, Vibration comfort

Raw materials: Produced, Recycled

Trims: Single function, multiple function, Multilayers

Simulation: Multilayered Charactersitics, Vibro-acoustic models


Single and Multilayered

Single elastic:

Steel

Single+Damping

Single+Porous

Single+Damping+Porous

Foam

Textile

RecycledFoam

Multilayered:

Double wall

P

o

r

o

u

s

M

a

t

e

r

i

a

l

s


Foams & Fibers Intrinsic Properties

Elastic

Porous-Foam

Kinematic viscosity

Fluid speed of sound

Fluidphysical

Fluid density

Fiber

Rigid

P

orous-Fiber

Limp

Porous

-Fiber

FluidB

ulk

Flow resistivity

Prandtl number

Specific heat ratio

Viscous characteristic length

Tortuosity

Porosity

Thermal characteristic length

Loss factor

Poisson ratio

Bulk modulus

Elastic

Bulk

Bulk density


Materials definitions and physical parameters

Material definitions

Fluids (air, water)

Isotropic solid (Structure Materials elastic havingsame properties in all directions):

steel, glass, etc.

Orthotropic solid (Structure Materials elastic withdifferent properties vs. directions):

composite

Damping Materials (unelastic):

septum, rubbers, EPDM, etc.

Mass materials (unelastic):

septum, rubbers, EPDM, etc.

Density, Insertion Loss, Transmission Loss

Spring like Materials:

Felts, Foam

Physical parameters

Density

Youngs Modulus

Poissons ratio

Damping Loss factor

Insertion Loss

Transmission Loss

Acoustic Absorption

Impedance

Porosity

Flow Resistance

Tortuosity

Complex Modulus

Bulk Loss Factor

01dB has solutions available to measureall above marked physical parameters?


Type of Data

Acoustic and Vibration materials properties cannot easily be found in bibliography

must be determined using different standards (ISO, SAE, ASTM, DIN, BS).

Each parameter is measured with an independent technology and with different equipment,

data format consistency in the data base


Type of Data

Data conversion

Density

Youngs Modulus

Poissons ratio

Damping Loss factor vs frequency typically FFT

Insertion Loss vs frequency typically 1/3 octavesTransmission Loss vs frequency typically 1/3 octaves

Acoustic Absorption vs frequency typically FFTImpedance vs frequency typically FFT

Porosity

Flow Resistance

TortuosityComplex Modulus vs frequency typically FFT

Bulk Loss Factor vs frequency typically FFT


Data conversion

PSD Normalization

It is possible to normalize the Frequency resolution of the measured spectrumdata by scaling it in PSD (Power Spectral Density units

It describes how Power of time series is distributed with frequency.

Practically is the squared Fourier transform, i.e. auto-power spectrum, dividedby frequency resolution in Hz.

It can be applied to spectra related to:Insulation IL or TL spectraDamping Loss factorAcoustic Absorption ImpedanceComplex ModulusBulk Loss Factor

[ ]f

aapsdaa

GG =


FFT to 1/3 octaves (Energy average)Transfer function derived FFTs are not necessarly concerned with Energy averaging, as it isthe case of an Acoustic absorption coefficient measured according to ASTM standards. In this case only the energy values of FFT lines corresponding to 1/3 octave center bandsare taken in account

Where Energy average is an issue, like Acoustic insulation spectra as IL or TL, FFT linesfrom the PSD spectrum are added together within a Frequency interval (F1 F2) corresponding to the given 1/3 octave filter

Definitions:

F = Frequency range

N = FFT lines

f = Frequency resolutionNs = minimum number of lines required for 1/3 octave filter

Fi = Frequency of i-th data sample

Minimum 1/3 octave band =

Example: F = 20 kHz, N = 3720, Ns = 3

1/3 octave band width = 21.5 Hz 100 Hz 1/3 octave filter

( )NFNs +1


Poro-acoustic parameters

Main parametersexperimental determination


Poro-acoustic parameters

Most common parameters:Impedance at 1!

2 general parameters:Sound Insulation TLSound Absorption 2 general cases:Randon incidence sound waveNormal incidence sound wave


Impedance definitions

Point Impedance (structures)

the ratio of the applied force to resulting velocity of response.

Typically, the force and velocity, both being vectors, the impedance is a tensor. The complex phase of a component of impedance indicates the relative phase of force tovelocity.

Impedance of acoustic materials (plane waves)Specific Acoustic Impedance (at x distance from a sample surface) is the ratio betweenpressure p(x,) to the normal component of fluid velocity un(x,)

),(),(

xuxp

Zn

=


TL RANDOM INCIDENCE: Sound Insulation IndexTransmission Loss ISO 140/x ISO 717/1 dBBati

mmaterialempty

VcTcT

VA f

= 4113.55

,60,60)(

Surface

Room Absorption

Room EmissionRoom Receiving

Partition

Which is this?

200 m3 Reverberant Room

RANDOM INCIDENCEAbsorption Ceefficient ISO 354 dBBati

( ) ====

+=

cLogmVST

V

SSA

ASLogLLR

mf

iif

ffReqfEeqfw

f

ff

1043.55

10

)(60

)(

10)(,)(,)('

)(

)()(

dBBati 6 channels Rw, NetdB


Transmission Loss TLInsertion Loss IL

2 small rooms on top of each other

2 alternatives:

dBBati 6 channels RwNetdB

dBFA server-TCP-IPExcel Macro TLSCS VS Application TLNetdB 4-12 channels, dB4 4 channels

Audio Ampllifier

Internal light absorption

Walls with TL of30 dB at 100 Hz

Microphones system

Steel plate and sample position

1

.

6

-

2

m


Transmission Loss TLInsertion Loss IL

Reverberant room and Semi-anechoic chamber

on top of each other

Audio Ampllifier

4 alternatives:

dBPower 10 channels - NetdB Lw,f (without-with sample) on steel plate = IL or TL

dBFA ISO9614 - NetdB, Symphonie Lw,f (without-with sample) on steel plate = IL or TL

dBBati 6 channels - NetdB TL/Rw

dBFA server-TCP-IP - NetdB 4-12 ch, dB4Excel Macro IL, TLSCS VS Application IL, TL


Insertion or Transmission Loss

Reverberant room in the ground

Acoustic transparence

Anecoichchamber

7 x 7 x 5 m


Absorption coefficient for random incidence: Small abs-cab

Walls with TL of 30 dB at 100 Hz

Internal high reflection

Loudspeakersystem

Amplifier system

RotatingMicrophone system

PC with DAQ-ANA System:Generator and analyzer

Ca 3 m

Ca 3 m

Ca 2.5 m

Lifting holes

Not yet available on dBFA.

Please ask for SCS 902A solution


Impedance Tube System

dBFA server-TCP-IPNetdB 4ch, dB4 , SymphonieSCS80FA Application , Zs, TL

Impedance of acoustic materials (plane waves)Specific Acoustic Impedance (at x distance from a sample surface) is the ratiobetween pressure p(x,) to the normal component of fluid velocity un(x, )Zs: Surface Impedance, Zc: Transfer impedance (complex)

),(),(

xuxp

Zn

=Microphonespositions

1 2

Sample

Sound Source

un

Zs ZcRigid wall

Microphonespositions

1 2


3 4

Sample

Sound Source1 or 2 Loads

(anechoicterminations)

un u*n

Audio Ampllifier

TL


Normal Incidence Absorption Coefficient

ISO standard 10534-2 it is not very good actually and we do not recommend to follow it in total.Our recommendation it is to use the positions M1 and M2 or M2 and MII which are the original positions in the earlier ISO and are also the best one in our experience.Mic. Positions R and MI have been introduced due to the latest revision of ISO 10534-2 which requires a higher Microphones distance for low frequencies. However, if you want to use position R, you shall move the sample about 15cm away to assure a minimum distance between the Mic. R and the sample. You just have to move backward the piston, it is very simple.

SCS9020B-standard tube (double)

RM2 M1 MII MI

Large Tube

M2 M1

Small Tube

R M2 M1 MII MI

Configuration of Impedance Tube for Normal Incidence Absorption Coefficient

Audio Ampllifier



dBFA Suite version 4.82 & 4.9Command line dbFA.exe --serverTransducers Data Base, Calibration, etc standard

Function FFT FRF Ref. Ch 1 (see Manual)

Display at user choice (no infoluence on the software)

Configuration of dBFA RT part for Normal Incidence Absorption Coefficient


Normal Incidence Absorption CoefficientTASKS:

CalibrationPerforms the phase adjustment between 2 microphones, including mics. 1 to 4 on the TL

MeasurementPerforms TF measurement

CalculationUse TF measurement to calculate and Zs

Recall DataRecall internal Data Base

Software SCS80FA - Alpha Measurementfor Normal Incidence Absorption Coefficient

Info and instructionto the user stepby step

GraphicDisplay

SCS80FA Main Panel

Link to dBFA/RT




SCS80FA COnfiguration




SCS80FA Results

Continous Frequencies FFT

1/3 octave bands




SCS80FA Results

Zs Surface ImpedanceRe/Im


Plane waves Transmission Loss TLLoudspeaker Test sample Anechoic end

p1 p2 p3 p4

A1B1

A2B2

d s2

x3

x4x1x2

s1

x

From the general definition of TL in which:

TL measurements in a tube is based on the Transmission Loss Matrix a unique parameter for each material.

We are interested just in the 1st term of the Matrix (f) which is the same as in the definition of TL

Notes:

Material sample with Symmetricthickness yeld to error in Cremermethod for calculating the Matrix Determinant

TL results with Kundt method are very similar to 2 rooms method

There are 4 waves to consider:The Forward travelling wave is defined by its incident part A1 and transmitted part B2

The Backward travelling wave is defined by its incident part A2 and transmitted part B1

And we can calculate the coefficient in terms of Sound Pressure p measured at each microphone positions at distance x

System of equations in 4 unknowns can be reduced to a two loads case in which the Sound Pressure (G1 autospectrum) p1 isassumed as reference for cross-spectra takenfor 2 measurements conditions, usingdifferent anechoic ends, indicated as pedixO and C ( )


Plane waves Transmission Loss TL

SCS9020B-standard tube for TL measurement

Transmission Loss measurement using Kundt Tube device are not covered byISO or ASTM standard

3 microphones method or single load TL Modulus only 4 microphones method or two-loads TL Mod, , Zc


1 2


3 4

Sample

Sound Source1 or 2 Loads

(anechoicterminations)

un u*n

Audio Ampllifier

dBFA server-TCP-IP - NetdB 4ch, dB4SCS80FA Application TL, Zc


Plane waves Transmission Loss TLTransmission Loss measurement using Kundt Tube device is very similar to Absorption mesurement


From ISO 10534 it can be seen that Sound absorption coefficient of the material can be determined using Standardized Kundt apparatus with 2 methods:SWT standing wave ratio and TF transfer function method

While the SWT intrinsically get to single Frequency values, steady state sinusoidal excitation, the TF is based on FFT and FRF so it get to expressed in a full spectrumA problem: how to derive 1/3 or 1/1 octave values from TF method?

Common sense says: take the values at the Frequencies corresponding to 1/3 octave bands nominal value!New methodology based on the measurement of the reverberation time in the tube.

It can be considered a kind of hybrid among ISO 10534 but it is more precise and energetically correct.The sound signal is an exponential sine sweep of which it is measured the Impulse Response Function IRF.

By convoluting the IFR with 1/3 octaves IIR we obtain the from a whole 1/3 octave bands and not just from a single Frequency line!

Kundt Tube extended metodologies (T60)

Sine Sweep IRF

Kundt device with add.on elements for T60


Kundt Tube extended metodologies (T60)

Available!As SCS 902A solution

Everything is compatiblewith standard Kundt device

Circled items are add-on forT60

Squared items are standard

Sample II

Sample I

LoudspeakerOnly 1 micorphone is necessary

Impulse Response (from T60 measurment) A new method for the measurement of single and coupled absorption coefficients It is based on the reverberation time in the Kundt tube The method produces 1/3 octave band sound absorption values and complies with ISO-ASTM results

but resolves ambiguities in the conversion of FFT values into 1/3 octave values. The sound energy is injected at side and moves in both directions and build up the standing waves After each impact of the plane waves with the samples at the ends the intensity of the waves is reduced

yelding to the concept of Reverberation Time Reverberation time (T60) is obtained from the measurement of the impulse response using a

methodology known as exponential sine sweep:

Squared Impulse Responseand Schroeder back-integration to evaluate the reverberation time in the tube with an exceptional S/N ratio.

F2

0.0

0.2

0.4

0.6

0.8

1.0

0 200 400 600 800 1000 1200 1400 1600 1800

Frequency [Hz]

RT TF

Comparison of results for 0using ISO-ASTM method (TF) and the Impulse Response(TF) for T60 evaluation

Transmission Loss measurements in a tube can also be performed.

The excitation signal is a sine sweep and the impulse response of each microphone position is determined. The maxima peaks shift of the measurements gives the distance x1 to x4 and the amplitude coefficient of the Complex Pressure function are determined and used to estimated the coefficient of Transfer Function Matrix


SCS-902A: Software suite (1) example


Poro-acoustic and Poro-elastic parameters

Additional parametersexperimental determination

Damping Loss FactorYoung ModulesDynamic stiffnessFlow ResistanceTortuosityBulk Modulus


Damping Loss Factor (SAE Method)

Instrumentedhammer

Accelerometers

Vibration testing

Available!For dBFA with TCP-IP commands on any 01dB platforms supported


Tensile elastic (Youngs) modulus

Shear modulus

Damping Loss factor

Poissons ratio computed from

the shear and elastic moduli provided.

The bulk elastic or Youngs modulus of the foam , when measured in a vacuum

for the bulk frame material.

Bulk Loss Factor

the complex part of the bulk elastic or Youngs modulus of the porous material, when measured in a vacuum. It is a unitless quantity that describes the percent oftotal energy that is lost to heat in the process of propagation.

Defined as: is the power lost to heatE is the total energy of the material

Youngs Modulus - Poissons Ratio

Oberst device SCS 902A / 9021* SAE device SCS 902A / 9022

Elost

=


Damping Loss Factor (Oberst Method)

Vibration testing



Damping measurements

Definitions

Resonance peaks of the beam plate are analysed with FFT analysis and damping coefficient can be derived from the Frequency Response Function FRF with 3 methods:

Half power frequency band at 3dB points

Circle fitting of resonance peaks (see figure at side)

Exponential decay of synthesized SDOF


Impedance, Dynamic Stiffness

Point Impedance (structures)the ratio of the applied force to resulting velocity of response (F/v).

Typically, the force and velocity, both being vectors, the impedance is a tensor. The complex phase of a component of impedance indicates the relative phase offorce to velocity.

Excitation can be provided by a small shaker (100-200 N) or by an Impact Hammer

Response is measured using an accelerometer (conversion to v by dBFA)


F a, v

sample

Smallshaker


Porosity:the density fraction of the porous material that is comprised of fluid.

Defined as:

where is the mass density.porous

solidh =1

Porosity & Flow Resistivity

Flow Resistivity: a measure of the resistance tofluid flowing through the porous material

Defined as:

where p is the static pressure differential acrossa layer of thickness x, and is the velocity ofairflow through the material.

x

p

vR

= 1

Flow resistivity device

SCS 902A / 9021


Flow Resistivity



SCS-902A: Software suite example for Flow Resistance


Tortuosity or Structure Factor: a unitless quantity relating the average fluidpath length through the material normalized by the thickness of the bulk foammaterial. Defined as:

Tortuosity is a measure of the deviation within the porous material of both the pore axis from the direction of wave propagation, and of the pores nonuniformity in cross-sectional dimension.

Tortuosity can also be expressed as a function of porosity h and impedance Z:

where is the porosity and Z the impedance

2

2 Re

=

fluid

absorber

ZZh

Tortuosity

absorber

fluid

RR =


Tortuosity



Bulk Modulus

Definitions

Bulk Modulus

Derived by measuring the transfer function between two accelerometers

Damping estimated on the system resonance as Df/f at 3 dB below peak

Mechanical Impedance method


Bulk Modulus


System to measure:

Young modulus static

Poisson ratio static

Young modulus dynamic

Dynamic stiffness

Damping Loss factor

Bulk modulus in vaccum


Vibro-acoustic materials parameters mesurement:

APPLICATIONS DOMAINS


Vibro-Acoustic Materials

Mass elementsinsulation

Elastic elementsinsulation

Limp filmabsorption

Textilesabsorption

Foamsabsorption

Septumdamping

I

n

s

u

l

a

t

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o

n

w

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o

u

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y

A

b

s

o

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p

t

i

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BUILDINGS

Concrete

Bricks

Steel plates

Honeycomb

Plywood

Wood panels

Rockwool

Glasswool

Glassfiber

PreformedVegetalfibers

Fabric

Textilelayers

PU Foam

StirolicRubber and EPDM

TRANSPORTATION

INDUSTRIES

Insulation

Skeleton & Absorption

Septum


Ceiling absorptionAbsorption coefficientISO 354 Rev.Room

Walls insulationTL Rw RwISO 140/717

Floors insulationTL impactISO 140-717

Vibration insulationLosss factorStiffness

Building Vibro-Acoustic Materials

And the winner is:NetdB + dBBati


Damping

PU FoamInsulationRubber & PU FoamEPDMPlywoodWoodstock

TL - damping

SeptumOberst -SAE

Transportation Vibro-Acoustic Materials

ScreenPU EPDMTL - Kundt

AbsorptionTextileKundt absorption

And the winner is: dB4/NetdB + dBFA


Industries Vibro-Acoustic Materials

InsulationSteelPU FoamGlasswool

TL, Normal Incidence & Z

AbsorptionGlasswoolFabricRandom incidence

DampingSeptumStiffness, Loss Factor

AbsorptionGlasswoolFabricNormal Incidence & Z

Workshop noise

Enclosures

Silencers

Vibration isolationRubberStiffness, Loss Factor

And the winner is: dB4 + dBFA


Environmental Acoustic Materials

Sound AbsorptionKundt tube low frequenciesImpulse method on site (Adrienne)

SPB Statistical pass-by ISO 11819-1CPX Close-proximity ISO 11819-2

Sound Absorption + TLImpulse method on site (Adrienne)

Sound Absorption + TLImpulse method on site (Adrienne)T60 to obtain

Sound Barriers

Tunnelling

Sound AbsortionAsphalt

And the winner is: SYMPHONIE + dBBati and dBFA

Whos winning now? .

customers material characteristics

Documents

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materials definitions

vibration materials

fftinsertion loss vs

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vibration comfortraw

fftimpedance vs frequency

fft8areva strategic