Study, by reflection, of input impedance under oblique incidence of slotted acoustic screen

Authors

  • V.J. Chvojka Ecole Polytech., Montreal Univ., Que., Canada
  • L.-P. Simard Ecole Polytech., Montreal Univ., Que., Canada
  • M. Amram Ecole Polytech., Montreal Univ., Que., Canada

Keywords:

noise abatement, acoustic noise, input impedance, oblique incidence, slotted acoustic screen, phase reversal sound barrier, slitted waveguides, phase reversal barrier, complex sound pressure

Abstract

A new type of phase reversal sound barrier composed of slitted waveguides has shown remarkable noise control properties in low frequency for a plane wave at normal incidence. In order to assess the overall performance (e.g. ground effect, variable source position, etc.) it was necessary to study the effect for obliquely-incident sound wave. Two methods based on reflexion measurements at oblique incidence were applied to study the input impedance of a phase reversal barrier. The first one, successfully used by Klein and Cops (1980), is a stationary wave method derived from that of the impedance tube. The second method presented by Ingard and Bolt (1951), consists of measurements of the complex sound pressure at a point of the sample surface. The results of the study show almost no angular dependence of the system input impedance (locally reacting system within ±40°) in the vertical plane (perpendicular to the slits). On the contrary, in a horizontal plane (parallel to the slits), this angular dependence becomes appreciably stronger

Published

1985-10-01

How to Cite

1.
Chvojka V, Simard L-P, Amram M. Study, by reflection, of input impedance under oblique incidence of slotted acoustic screen. Canadian Acoustics [Internet]. 1985 Oct. 1 [cited 2021 Dec. 5];13(4):25-43. Available from: https://jcaa.caa-aca.ca/index.php/jcaa/article/view/553

Issue

Section

Technical Articles