Acoustic Backreaction on Sound Sources in Ducts

Analysis of Acoustic backreaction on a sound source is of fundamental importance for measurements in duct acoustics. In this paper, a preliminary analysis of the problem is presented. For the purpose of analysis, a source is considered to be a combination of an ideal source (such as monopole, dipole, or quadrupole), in series with a constant impedance. It is shown that the relative magnitude of the source impedance would lead to the more familiar idealizations such as constant velocity or constant pressure source. The backreaction is shown to be strongly dependent on the length of the duct. The backreaction for higher-order modes is more prominent near their cutoff frequencies and wall absorption strongly influences its magnitude.