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MASTER "MECANIQUE, PHYSIQUE ET INGENIERIE" ,Spécialité Recherche "Acoustique" (M2)

Deuxième phase: Modules spécialisésS5 : Contrôle actif et milieux poreux (Cédric MAURY)S5 : Contrôle actif et milieux poreux (Cédric MAURY)

Teresa Bravo MaríaTeresa Bravo Marí[email protected]

Contrôle Actif Acoustique

Schedule

I. Wednesday 8:30 – 12:30Theory of Active Noise Control (ANC)Exercises

II Thursday 8:30 – 10:30II. Thursday 8:30 10:30Theory of ANC

Thursday 10:30 12:30Thursday 10:30 – 12:30Real-life applications of ANC

III. Thursday 13:30 – 15:30Firts practical exercise ANCp

Thursday 15:30 – 17:30Second practical exercise ANC


Seco d p act ca e e c se NC

Real-life applications of Active Noise Control

Direct ApplicationsA i N i C l i f fi ldActive Noise Control in free fieldActive Headset (ear defender)Active Noise control in ducted systemsActive Noise control in ducted systemsActive Noise Control inside planes, vans and cars

Further applications of active control techniquesE i t l th i f d fi ld iExperimental synthesis of random pressure fields in laboratory conditionsThe reproduction of a random pressure field in aThe reproduction of a random pressure field in a transmission suite for the determination of the TL of a partition


Active Control of Transformer Noise, Conover 1956


Active Headset, (Carme 1988)


Active Headset (deAlba and Cobo, 1999)

15

20

5

10

Ate

nuac

ión

(dB

)

-5

050 63 80 10

0

125

160

200

250

315

400

500

630

800

1000

Frecuencia (Hz)


The design of near field acoustic arrays for audio applications

Institute of Sound and Vibration ResearchUniversity of Southampton, UK

Minimisation of interference between two people listening to different audio signals using loudspeakers in the headrests of adjacent seats.audio signals using loudspeakers in the headrests of adjacent seats.

Listening to channel 2 Listening to channel 1Listening to channel 2 Listening to channel 1

Dark zone Bright zone

Acoustic array


Active control in ducted systems

Sin CAR

Con CAR


Active control in ducted systems

-40

-20

0

100

-80

-60

SP

L(dB

)

0 100 200 300 400 500 600 700-140

-120

-100

f(H )


f(Hz)

Active Control of the noise transmitted through a windowwindow

(Kaiser et al, 2001)


Implementation of a multi-channel Active Noise Control System

Identify the dominant noise sources and the propagation paths.

Id tif th t f i t ti l t d i t b ti

y

Identify the type of noise: stationary, correlated, main perturbation frequency range

.

Determine the coherence between the noise and the reference signals.Place the sensors so the coherence would be the closest to unity.

Determine the sound pressure levels. Choose the actuator type. Place the optimal positions for control sources and error sensors.

Use the electronic control system to select a feedback or a feedforward control system, the sampling frequencies, the filters to apply…y , p g q , pp y

Select different types of algorithms, different coupled control systems, different control parameters etc


different control parameters, etc.

Active Sound Control in a propeller aircraft

System is standard fit onSystem is standard fit on the Dash 8 Q400(Stothers et al., 2002) P i di it ti f( , ) Periodic excitation of

fuselage by propeller(www.bombardier.com)


(www.bombardier.com)

Active Sound Control in a propeller aircraft(Stothers et al., 2002)( , )


Typical performance of an Active Sound System(Stothers et al 2002)(Stothers et al., 2002)


Active system with structural actuators


Active Control of Sound inside a van

Design and physical implementation of an active noise control system for control of the engine booming in a cabin vanfor control of the engine booming in a cabin van


Active Control of Sound inside a van


Experimental results at the error sensor positions100

80

90

(dB

)

50

60

70

SP

L (

2000 2500 3000 3500 400040

50

R.P.M

What is the effect of the control 76

78

80

82

)What is the effect of the control system out of the error sensor positions ?

70

72

74

76

SP

L (d

BA

)

Is the system robust to disturbances in the plant and the excitation ?

2000 2500 3000 3500 4000 4500

66

68

70


RPM

Local active control system inside a car (Elliott et al, 1986 )


Robust optimisation of the active system12 19 26 33 40 47 54

4

5

10

11

12

17

18

19

24

25

26

31

32

33

38

39

40

45

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47

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54

2

3

8

9

15

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22

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29

30

36

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43

44

50

51

1

6

7

13

14

20

21

27

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34

35

41

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48

49

A2A4

A6A8

A9 A10

A1

A5

A3 A7


Optimisation of the physical part by means of natural algorithms

Classical optimisation methods: steepest descent algorithmsteepest descent algorithm

For the cost function in our problem (attenuation values) weproblem (attenuation values) we obtain a non-linear problem that cannot be solved by classical algorithms


Exhaustive search

dB 1 2 3 4 5 6 7 829 0 0 0 0 0 0 0 028 0 0 0 0 0 0 0 027 0 0 0 0 0 0 0 026 0 0 0 0 0 0 0 325 0 0 0 0 0 0 4 6324 0 0 0 0 0 1 29 20323 0 0 0 0 0 13 114 39222 0 0 0 0 2 26 221 74721 0 0 0 0 11 117 444 93320 0 0 0 1 29 200 517 76319 0 0 0 7 64 189 445 73518 0 0 1 18 55 131 372 83517 0 0 1 0 17 153 554 99317 0 0 1 0 17 153 554 99316 0 0 0 2 49 344 939 128615 0 0 0 17 130 408 772 96314 0 0 3 22 100 378 875 112313 0 0 1 19 146 480 880 88112 0 0 0 14 109 465 950 82811 0 0 1 34 219 662 982 74010 0 0 3 56 292 802 1050 6619 0 1 15 87 431 986 975 3828 0 0 10 163 671 1016 629 1888 0 0 10 163 671 1016 629 1887 0 1 40 291 685 695 344 916 0 9 90 304 496 432 204 535 0 13 101 266 348 271 100 74 2 20 62 163 222 137 35 0


3 1 18 86 174 181 87 5 02 2 11 68 140 105 15 0 01 3 38 77 42 6 0 0 00 8 9 1 0 0 0 0 0

Selection of the optimal configuration

Selection of the optimal positions by using the simulated annealing algorithm


Experimental resultsRobust optimisation for global control at the head heights

Active Control

Original field

Robust optimisation


Feedback Control System for Narrowband Control of Boom in a Car(Honda, 2001)


Other applications of active control techniques

The experimental synthesis of random pressure fields in laboratory conditions with an array of near-field loudspeakers:

Diffuse fieldDiffuse field

Plane Wave field

Turbulent Boundary Layer pressure fieldpressure field


Synthesis of a Turbulent Boundary Layer


Synthesis of a diffuse pressure field

(ωΠ

)

Sound Transmission Testing at Low Frequencies

(dB)(ωΠ

(ωΠlog10R(ωtrans

inc10

)))

Diffuse field (theory)

0.8

1

Diffuse field (theory)Diffuse field (model)

)cossinsincossin( zyxjktjeP

0.4

0.6

n fu

nctio

n

)( yjjinceP

0

0.2

Spa

tial c

orre

latio

0 0 5 1 1 5 2 2 5 3 3 5 4

-0.4

-0.2


0 0.5 1 1.5 2 2.5 3 3.5 4Distance divided by acoustic wavelenght (d/)

Experimental set-up

R i i

Z2

Z1

Receiving roomSource room

Y1

Y2

XOX1

X2O2

O1

s

rec

p10recsource A

slog10LLR


Sound reduction index with the sound intensity method

Source room Receiving room

p2source

Sound Intensity Microphone Probe


The reproduction of a diffuse field with an array of loudspeakersof loudspeakers

dD

ex

yW G yW G

x)WGD(yde

DGDG]GG[W †1 HHopt


Experimental verification

45

50

B)

30

35

40

on In

dex

(dB

15

20

25

und

Red

uctio

14 22.4 35.5 56 90 140 224 355 561 9005

10

15

F (H )

Sou


Frequency (Hz)

Th kThank youy


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