title: Low frequency sound attenuation in a flow duct using a thin slow sound material.
abstract: A thin subwavelength material that can be flush mounted in a duct and that gives an attenuation band at low frequencies in air flow channels is presented. To decrease the material thickness, the sound is slowed in the material using folded side branch tubes. The impedance of the material is compared to the optimal value given by the Cremer condition, which can differ greatly from the air characteristic impedance. Grazing flow on this material increases the losses at the interface between the flow and the material.
authors.affiliation: Laboratoire d'Acoustique de l'Université du Maine, Unite Mixte de Recherche 6613, Centre National de la Recherche Scientifique, Av. O Messiaen, F-72085 LE MANS Cedex 9, France yves.auregan@univ-lemans.fr.
authors.forename: Yves
authors.initials: Y
authors.lastname: Aurégan
authors.affiliation: Sound and Vibration Laboratory, Faculty of Engineering, Ain Shams University, 11517 Cairo, Egypt maazfarooqui@gmail.com.
authors.forename: Maaz
authors.initials: M
authors.lastname: Farooqui
authors.affiliation: Laboratoire d'Acoustique de l'Université du Maine, Unite Mixte de Recherche 6613, Centre National de la Recherche Scientifique, Av. O Messiaen, F-72085 LE MANS Cedex 9, France Jean-Philippe.Groby@univ-lemans.fr.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Groby