Solving the wave equation on a disk gives a solution in terms of Bessel functions.
Wave Equation--Disk
See also
Wave Equation, Wave Equation--1-Dimensional, Wave Equation--Rectangle, Wave Equation--TriangleCite this as:
Weisstein, Eric W. "Wave Equation--Disk." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/WaveEquationDisk.html