Each speaker stack radiates a spherical wave with geometric (1/r) spreading. The pressure at any point is the real superposition of every source, each carrying its own acoustic travel-time delay r/c and an optional electronic delay (the "delay-tower skew" real PA engineers dial in to time-align stacks):
p(x,y,t) = Σᵢ [Aᵢ /(1+rᵢ/R₀)] · sin(2πf(t − rᵢ/c) + φᵢ)
k = 2πf / c, λ = c / f, c = 343 m/s
φᵢ = −2πf · delayᵢ (electronic skew, ms)
Where crests from different stacks arrive in phase the field brightens (constructive interference); where a crest meets a trough it cancels (destructive). This is the same low-frequency alignment problem sound engineers fight at real festivals — the field you see recomputes every frame from the formula above, it is not a texture.
The listener readout uses the steady-state phasor sum Σᵢ Aᵢ·e^{j(−k·rᵢ+φᵢ)} so the SPL number stays stable instead of flickering with the animation phase.