ATPA, Advanced Transfer Path Analysis Method

ATPA - Advanced Transfer Path Analysis -

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Use ICR ATPA

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• ATPA: BACKGROUND

• ATPA & OTHER METHODS

• PROCEDURE STEPS

• APPLICATIONS

• PRODUCT

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ATPA:

BACKGROUND

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• ATPA is an advanced tool for the vibro-acoustic diagnostics that provides

information on the contributions to the overall noise of each element to study.

•ATPA is the only product capable of providing information on the source

contributions both regarding coherent and noncoherent addition.

•ATPA is a product exclusively created, developed and lauched onto the market by

ICR.

• ATPA is a reference product for the railway manufacturers being used for Alstom

and CAF.

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B A

The origins of ATPA lie in the need to solve two different problems:

•Determining the noise produced by each one of the forces acting on a mechanical

system (TPA).

•Quantifying the contribution of each part of a vibrating system to the total noise

measured at a given location

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60’s The method of solving the problem A was to cover all the interior of the vehicle

with heavy acoustic isolating materials and after to uncover the surfaces one by

one. Was the called Strip method.

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Strip-tease 1975

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60’s The method of solving the problem B was to completely unlink the engine

from the car by supporting it with external elements and after to link the

engine supports to the car one bye one.

The forces are not really found by this method but their effects on the noise

are quantified.

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•Transmission path analysis methods started at the mid 70’s with the work on

MIMO (Multiple Input Multiple Output) systems by Potter, Bendat, Piersol, Dodds

and Robson among others. The MIMO approach aims at computing the set of

optimum values that best fit real measured data. As a such, it only requires

operational measurements and can hence be classified as a one step method.

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70’s MULTIPLE COHERENCE METHOD

R.J. Alfredson, L.L.Koss, J.Bendat,C.J. Dodds and R.Potter

1 1 2 2 ...... n np a H a H a H

Applying this equation in a set of different times we can calculate de Hi

values in a least square error sense. This allows to know the contributions

of each subsystem to the interior pressure (SPL).

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•At the early 80’s, Magrans (J. Sound Vibr.) defined the force TPA approach in its

nowadays format as well as the basis for the ATPA (Advanced TPA) that will be

exposed in this presentation.

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80’s GTDT Method

The only measurable TF is the GTF (Global Transfer Function).

The signal flows through all subsystems and all of them contribute to the SPL.

These contributions are not superimposable.

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80’s GTDT method (Magrans, J.S.V. 1980)

The Paths are defined using the DTF (Direct Transfer Function).

This DTF is not measurable but is the only TF that we can use to know the

interior pressure by superposition of subsystems contributions.

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80’s GTDT method

DTFs TD can be computed from the measured GTF TG

GTDT method

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With only the GTF >Forces TPA

Equivalent to the engine unlink old method

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With DTF>ATPA using acceleration

Equivalent to the old strip method

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Forces TPA

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ATPA

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Acoustical example: Helmholtz equation on a 2D rectangular space.

GTF DTF

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•TPA with the Forces/acceleration Global Transfer function speaks only about

the external Forces and his contribution to the noise or vibration in the object, not

about “paths”. The black box remains closed. It is a “sensitivity “ method.

•ATPA with the DTF speaks about the paths that links the subsystems in the test

object.

•Also through the DTF we can know how the vibration or noise of a subsystem

contributes to the noise or the vibration in another subsystem.

•ATPA opens the black box , ATPA works with “signals” (acceleration, velocity,

displacement, Energy).

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ATPA & OTHER METHODS

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• Other’s TPA only works in coherent identification (low frequency).

• ICR ATPA provides information on the contribution of all frequency ranges,

coherent and energy identification (high and low frequency).

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• TPA implies time dismantling part of the system and can produce fundamental

changes to the structure such as a reduction of the stiffness in the area

surronding a connection.

• ATPA is an easy and fast method and enables measurements to be made on

the full system without dismantling anything.

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•TPA allows to determine

the contribution to the

overall noise that is due to

the force acting on the

wheel.

•TPA does not give

information on the particular

contribution of each

structural component or

subsystem.

•ATPA gives this information

because quantifies the

transmission path of each

element of any structure.

F F

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F SPL

F a0

a1

a2 a5

SPL a4

a3

In summary,

• Classic TPA acts as a

black box connecting an

input force with an SPL

output.

• ATPA quantifies the vibro-

acoustic connections

(transmission paths) among

various subsystems and

evaluates their mutual

interaction.

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•The results of LMS and Brüel & Kjaer Reciprocity methods only represents the

reality when panels are unlinked, if not the results will superimposed because is a

global transfer.

•When the source is the panel the signal will arrive from everywhere to the

microphone that has replaced the source, like it arrives , in the direct experiment ,

from the source to the to the panel.

• The measured values are global transfers and can’t be superimposed

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•Microflown Reciprocity method has no error in the theory (Daniel Fernandez Comeñasa,

Andrea Grosso, Jelmer Wind, Hans-Elias de Bree and Keith Holland. Further Development TPA: Scan & Paint TPA as a fast tool for

Sound Source Ranking.SAE International (2012) but shows that the result obtained is not which is

wanted. The paper result is that we can know the pressure in a point (i)

measuring by reciprocity μ and β and the presures and accelerations in operational

mode a (acceleration) and p (pressure) in all subsistems..

k

kkkkrapp

• But this is a not relevant physical state and by the way is not the strip case.

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• ATPA really identifies the elements which contributes to overall noise as the

“Strip”, which applied the superposition principle which can be expresed with this

formula:

k

kkrap

• This is the Strip situation, only one panel radiating and the others blocked.

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PROCEDURE STEPS

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1 2 31 32

1 2

31

32

Step 1:

STATIC TEST

CROSS FUNCTIONS ANALYSIS

Step 2:

OPERATING

TEST

OPERATING DATA RECORDING

1

2

31

32

Step 3:

COMPUTATION

OPERATING

CONTRIBUTIONS

ANALYZER

RECORDER

…

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APPLICATIONS

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RAILWAY

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Objective: To reduce the noise inside a train passengers area.

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Measured Spectrum vs Synthesised

10

20

30

40

50

60

70

80

20

150

280

409

539

669

798

928

1058

1188

1317

1447

1577

1706

1836

1966

2095

2225

2355

2484

2614

2744

2873

3003

3133

3263

3392

3522

3652

3781

3911

4041

4170

4300

4430

4559

4689

4819

4948

Hz

dB

Synthesised

Measured

Averaged narrow band results

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dBA

4952

4645

4857

4852

4155

435252

5042

4539

5252

4545

5149

4752

4754

5148

5250

4246

3845

4644

7066

6558

4446

5858

6668

7576

30 35 40 45 50 55 60 65 70 75 80

Low_Pan_A_e1-01

Window_A_e1-04

Window_A_e2-07

Up_Pan_A-10

Roof_cor_A-13

Roof_A-16

Low_Pan_B_e2-19

Side_Win_B_e1-22

Side_Win_B_e2-25

Up_Pan_B_e2-28

Roof_cor_B_e2-31

Roof_B_e2-34

Roof_cnt_e2-37

Floor_A_e2-40

End1_Panel_B-43

Ctrl_1

Target_Mic-48

Averaged dBA results

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4.6644 4.6646 4.6648 4.665 4.6652 4.6654 4.6656 4.6658 4.666

35

40

45

50

55

60

65

70

Time history dBA Comparison. from t:4.6636 s. to t:4.666 s.

t [s]

dB

A

Synthesised

Target-Mic-48

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Low frequency results

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Low frequency results

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Objective: to reduce the noise inside a train cabin.

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60 65 70 75 80

Armario

Techo

[30]MicroChapaInferiorFrontal

[31]MicroVentilaciónDrontal

Resto

[29]MicroChapaBajoPupitreDerecho

[28]MicroJuntaPuertaInterior

[26]MicroVentanaDerecha

[9]Suelo

[32]Sintetizado

[33]Medido

dBAs Promedio Grupos

61(61)

63(65)

68(70)

69(73)

70(74)

70(76)

73(78)

75(80)

75(81)

81(81)

81(81)

Original Noise: 81 dB

Final Noise: 76 dB

Result: Interior cabin noise reduced in 5 dB B

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1

2 3

4

5

6

Case 1

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Initial, prediction and measured

Case 2: prediction and solution of vertical damper problem

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BUILDING

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Objective: to identify and solve the problems of UNE EN ISO 12354 standard in determining

contributions of direct and indirect sources.

Configuration 1

Configuration 2

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Reconstruction for configuration 1 Reconstruction for configuration 2

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Objective: study of noise transmission paths in windows through frames, the joints

between window and frams, the joints between glass and frames, etc.

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WIND POWER

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Objective: study the aerial and structural contribution of two ventilation pipes in case of

noise emitted by a wind turbine.

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Valores Globales en dBA

40

45

50

55

60

65

50 Hz 40 Hz 35 Hz 30 Hz 25 Hz 0 Hz

Modo Funcionamiento

dB

A

Medido

Sintetizado

Ruido de Fondo

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PLOTTER

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Objective: reduction of a plotter radiated noise.

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Narrow Band Results

dBA Results

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PRODUCT

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50-hour course whereby the transmission paths are established and assessed

through Direct Transfer.

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The “subsystem” concept, which is essential in the ATPA application, is defined as

well as the theoretical basis.

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ICR usually works for 30 working days in conjunction with the client´s staff to

perform a series of tests that may show how the method works and provides the

client with the physical principles governing the method.

A Measurement Protocol is the final document of the Know-How transfer

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• ICR provides its

software in compiled

Matlab and also

programs the input

processing for specific

files of the client in

Matlab.

• The software is custom

designed for each client

so that its application

matches their needs.

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•Taylor-made application

•Sources contribution: Classical TPA method.

•Emitters contributions: Advanced TPA method.

•Frequency range from 0 to 5 kHz.

•Not required to measure forces (#LMS, Brüel &

Kjaer).

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Only the leading manufacturers of rolling stock

use ICR ATPA method

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Use our ATPA method

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