A new type of acoustic liner developed for broadband noise reduction in flow ducts is considered in this paper. It combines passive absorbent properties of a porous layer and active control at its rear face. The complete design procedure of this hybrid passive/active liner is developed here. The passive part is first considered with the determination of a suitable porous material and the cut-off frequency separating the active low frequency regime from the passive high frequency one. The control system is then presented: a digital adaptive feedback control is performed independently cell by cell, allowing an easy subsequent increase of the liner surface. The entire optimization process has been successfully applied to a laboratory flow duct: both predictions and measurements show the interest of the hybrid liner to reduce the noise radiation.


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    Title :

    Hybrid passive/active absorbers for flow ducts


    Contributors:

    Published in:

    Applied Acoustics ; 66 , 6 ; 691-708


    Publication date :

    2005


    Size :

    18 Seiten, 15 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English




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