  In this paper we simulated self- and mutual- acoustic impedances of guided
modes at the aperture and estimated accuracy of the piston radiation
approximation. We used the Rayleigh integral to simulate the interactions
between different guided modes at the aperture, with low time-consuming. This
kind of guided-wave technique can be utilized to solve problems in diverse
fields of wave science such as acoustics, electromagnetism and optics. For
acoustic waves emitted through a horn or a waveguide with an aperture much
smaller than the wavelength, there are only plane wave modes in the waveguide
and the aperture of horn can therefore be considered as a piston radiator.
However if an acoustic wave with high frequency such as ultrasonic wave is
radiated, there can exist several guided modes in the duct. For arbitrary shape
and size of waveguide, interactions between different modes must be taken into
account to evaluate sound field in the duct and total acoustic power from its
aperture. In this paper we simulated self- and mutual- acoustic impedances of
guided modes at the aperture and estimated accuracy of the piston radiation
approximation. We used the Rayleigh integral to simulate the interactions
between different guided modes at the aperture, with low time-consuming. This
kind of guided-wave technique can be utilized to solve problems in diverse
fields of wave science such as acoustics, electromagnetism and optics.
