2D Drum Resonance Modes

ψ_mn(x,y,t) = sin(mπx)sin(nπy)·cos(ω_mn·t)

Rectangular membrane (Dirichlet BC: zero at edges). Mode (m,n) has frequency ω_mn = π√(m²+n²). Color: red = +displacement, blue = −, black = nodal lines (zero). Degenerate modes: ω_mn = ω_nm.