where fr is the resonant frequency of the diaphragm;
it is a function of the material characteristics
(elasticity, E; density, ρ; and Poisson’s ratio, ν) of
the diaphragm, and the dimensions (thickness, t, and
radius, r) of the diaphragm. The constant λ has value
0.412 for circular edge-clamped diaphragm [14,15].