Bifurcation diagram and time domain simulations of the two harmonic resonance air column (parameter’s values in Tab. 1 with Z₂ = Z₁/1.5 or with Z₂ = 0, and Inh = 0) with respect to the control parameter γ. Upper plots: six time domain simulations of the dimensionless pressure p = p₁ + p₂ calculated between t = 0 and t = 0.5 s for γ = 0.32, γ = 0.36, γ = 0.40 (two simulations with different initial conditions), γ = 0.45 and γ = 0.53. The dimensionless pressure of the plots numbered from 1 to 3 (respectively 4 to 6) is displayed between −0.3 and +0.3 (respectively −1.2 and +1.2). Lower plot: Maximum of the absolute value of the periodic solution p over one period with respect to γ. The branch in green (respectively in black) corresponds to the case Z₂ = Z₁/1.5 (respectively Z₂ = 0), and illustrates an inverse (respectively direct) Hopf bifurcation scenario. Stable (respectively unstable) solutions are plotted with thick (respectively thin) lines. For each scenario, the Hopf bifurcation point where the equilibrium becomes unstable, is noted γ_thr. In the case of an inverse bifurcation the subcrital threshold γ_subthr is highlighted with a vertical dashed line.