Inducing a nonreflective airborne discontinuity in a circular duct by using a nonresonant side branch to create mode complexity

Yongxiong Xiao, Huancai Lu, D. Michael McFarland, Alexander F Vakakis, Lawrence A. Bergman

Research output: Contribution to journalArticle


A nonreflective airborne discontinuity is created in a one-dimensional rigid-walled duct when the mode complexity introduced by a nonresonant side branch reaches a maximum, so that a sound wave can be spatially separated into physical regions of traveling and standing waves. The nonresonance of the side branch is demonstrated, the mode complexity is quantified, and a computational method to optimize side-branch parameters to maximize mode complexity in the duct in the presence of three-dimensional effects is presented. The optimal side-branch parameters that maximize the mode complexity and thus minimize reflection are found using finite element analysis and a derivative-free optimization routine. Sensitivity of mode complexity near the optimum with respect to side-branch parameters is then examined. The results show reflection from the impedance discontinuity in the duct can be reduced nearly to zero, providing a practical means of achieving a nonreflective discontinuity for a plane wave propagating in a duct of finite length.

Original languageEnglish (US)
Pages (from-to)746-755
Number of pages10
JournalJournal of the Acoustical Society of America
Issue number2
StatePublished - Feb 1 2018


ASJC Scopus subject areas

  • Arts and Humanities (miscellaneous)
  • Acoustics and Ultrasonics

Cite this