# Acoustic Dipole in a Duct

Acoustic Dipole in a Duct

An acoustic dipole oriented along the axis is placed in a duct. The dipole can be moved along the axis. The resulting sonic radiation can be approximated by an -term Fourier series, given in the Details section, with representing the Helmholtz number (the cut-off frequency of a duct, product of the wavenumber and the duct radius) in multiples of .

x

y

m

k'

π/2