Radiation from a rectangular opening occurs in a variety of contexts, including organ pipes and horn drivers. This section derives an analytic expression for the radiation impedance resulting from the coupling of higher order modes in a rectangular pipe terminated in an infinite flange according to Kemp et al. [39]. Horn drivers mounted in loudspeaker cabinets are expected to be particularly suited to the infinite baffle approximation.
The radiation impedance for the modes of simply supported rectangular plates is also closely related to the current problem and is reviewed in Nelisse et al. [53].