Compact acoustic quadrupole Mach-number scaling
= Compact acoustic quadrupole Mach-number scaling
{title2=$\rho'/\rho_0=O(M^4\ell/r)$}
For a low-<Mach number> source with stress $O(\rho_0U^2)$ and advective time $\ell/U$, the three-dimensional compact <acoustic quadrupole> has density amplitude $O(\rho_0M^4\ell/r)$, where $M=U/c_0$. The power depends on these source-time and stress hypotheses, not only on the quadrupole label.