  In the physics lessons on waves and resonance phenomena in high school and
college, we usually consider sound waves in a tube with open or closed ends
\cite{ResnikHalliday}. However, it is well known that we need a tube with open
end correction $\Delta L$. The correction for a flanged circular tube was first
given by Rayleigh \cite{Rayleigh} and experimentally checked by several authors
\cite{exp}. In this paper, we show the different methods of obtaining the end
correction for a circular tube by a diffusion process.
