Active enhancement of the absorbent properties of a porous material

Thenail, D.; Galland, Marie‐Annick; Sunyach, M.

doi:10.1088/0964-1726/3/1/004

Cited by 13 publications

(11 citation statements)

References 5 publications

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“…Thus, the performance of the sound-absorbing system with an actively induced pressure-release condition at the back of the absorbing layer is very sensitive to the thickness of the absorbing layer. This fact was also observed by Thenail et al 2 On the other hand, for the impedance-matching condition, absorption decreases slowly as the thickness, l a , is increased, i.e., the system is insensitive to the absorbing layer thickness. Figure 3 also shows that the impedance-matching condition outperforms the pressure-release condition in most situations, in particular for thin layers.…”

Section: Nϭ123 ͑1͒supporting

confidence: 72%

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A new hybrid passive–active noise absorption system

Beyene

Burdisso

1997

The Journal of the Acoustical Society of America

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A new hybrid passive/active system is developed for sound absorption over a wide frequency range. The system is comprised of a layer of absorbing material positioned at a distance from an active wall, leaving an air space. The motion of the active wall is based on a new control approach which consists of the minimization of the reflected wave within the airspace which modifies the layer's back surface impedance so as to match the characteristic impedance of air. This technique is referred here as inducing an impedance-matching condition. Both numerical and experimental results of such a system are presented for normally incident planar waves. The hybrid passive/active system results in a high absorption coefficient of .8-1.0 over the frequency range 100-2000 Hz and is insensitive to system parameters such as air space depth and absorbing layer thickness.

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Section: Nϭ123 ͑1͒supporting

confidence: 72%

“…Thenail et al 2 investigated an active system that included a fiberglass absorbing layer backed by an air cavity terminated with an active surface. Their work was intended to show that a pressure-release condition on the back surface of the fiberglass leads to improvement in absorption.…”

Section: Introductionmentioning

confidence: 99%

A new hybrid passive–active noise absorption system

Beyene

Burdisso

1997

The Journal of the Acoustical Society of America

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“…So-called "hybrid" absorbers have thus been studied, combining absorbing materials and transducers driven so that the resulting device exhibits the performances of a conventional passive lining at higher frequencies and suitable performances at lower frequencies. Such systems have also been thoroughly investigated, with varying combinations of passive material, actuator, and control strategies [14,15,16,17,18,19,20].…”

Section: Introductionmentioning

confidence: 99%

Active Control in an Anechoic Room: Theory and First Simulations

Habault¹,

Friot²,

Herzog³

et al. 2017

Acta Acustica united with Acustica

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International audienceNoise control and source design require the measurement of sound radiation at lowfrequencies. Anechoic rooms, which are designed for this purpose, allowe cho-free measurements at medium or high frequencyb ut passive wall treatment is less effective at lowf requencya nd in practice no facility provides anechoicity below5 0Hz. This paper discusses the applicability of an active control algorithm which has been previously introduced to minimize the echoes from ascattering object to the cancellation of the lowfrequencywall echoes in an anechoic room including wall-embedded secondary sources. At first the paper discusses, in the general case then for afree half-space as amodel case, the algorithm keywhich consists in estimating the scattered acoustic pressure from total pressure measurements. Boundary Element Method computations are secondly used to simulate estimation and active control of error signals accounting for the low-frequencyscattered pressure in an anechoic room. The simulations showt hat control with af ew dozen microphones and noise sources allows al arge reduction of the noise scattered from the walls at low-frequency

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“…Thenail et al 2 also investigated a hybrid absorption system making use of a fiberglass absorbing layer backed by an air cavity terminated with an active surface. A pressurerelease condition on the back surface of the fiberglass was generated, resulting in increased absorptivity over a frequency range from 200 to 800 Hz.…”

Section: Introductionmentioning

confidence: 99%

A broadband passive–active sound absorption system

Smith

Johnson

Burdisso

1999

The Journal of the Acoustical Society of America

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In recent years, hybrid absorption systems have been implemented which achieve high sound absorption over a broad frequency range. This work is an experimental study of a broadband hybrid absorption system which is comprised of a layer of sound-absorbing material ͑the passive component͒ positioned at a distance from a movable wall ͑the active component͒ inside an impedance tube. The movable wall is used to impose desired boundary conditions in the cavity behind the passive layer, thereby increasing the absorption of the system at frequencies where the passive material is not independently effective. Both pressure-release ͑i.e., minimizing the pressure at the back surface of the layer͒ and impedance-matching ͑i.e., minimizing the reflected wave from the layer͒ boundary conditions are studied. The performance of the hybrid system for these two boundary conditions is compared for broadband disturbances over a frequency range of 100-1000 Hz. The unmodified passive system showed absorption coefficients greater than 0.7 only above 500 Hz, while the impedance-matching condition yielded absorption coefficients of 0.8 to 1.0 over the 100-1000-Hz range. The impedance-matching condition provided significantly better absorption than that achieved with the pressure-release condition. The sensitivity of these control approaches to system parameters is also investigated.

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Active enhancement of the absorbent properties of a porous material

Cited by 13 publications

References 5 publications

A new hybrid passive–active noise absorption system

A new hybrid passive–active noise absorption system

Active Control in an Anechoic Room: Theory and First Simulations

A broadband passive–active sound absorption system

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