Mesh for Acoustic Analysis

What is appropriate mesh size of the acoustic analysis?

In order to maintain the accuracy of the acoustic analysis result, you must have the mesh size to 20 split the wavelength of the maximum frequency to be analyzed.
Mesh size ⊿X = <lambda / 20, lambda = A / F
(lambda = wavelength, a = speed of sound, F = maximum frequency to be determined)

For more details on mesh size for acoustic analysis and example, refer to this document.