By adding a particle source term in the Boltzmann equation of kinetic theory,
it is possible to represent particles appearing and disappearing throughout the
fluid with a specified distribution of particle velocities. By deriving the
wave equation from this modified Boltzmann equation via the conservation
equations of fluid mechanics, multipole source terms in the wave equation are
found. These multipole source terms are given by the particle source term in
the Boltzmann equation. To the Euler level in the momentum equation, a monopole
and a dipole source term appear in the wave equation. To the Navier-Stokes
level, a quadrupole term with negligible magnitude also appears.Comment: 5 pages, to be published in Proceedings of the 36th Scandinavian
Symposium on Physical Acoustic
