Top and bottom plots represent respectively the maximum amplitude of the periodic oscillation branches and their oscillation frequency versus the blowing pressure. Left: case H = h₀; right: case . Blue curves: case  = 165.84 Hz (left) or 167.75 Hz (right); orange curves: case  = 164.00 Hz (left) or 165.17 Hz (right); green curves: case  = 175.09 Hz, which corresponds to an arbitrary value at which the Hopf bifurcations are direct. The line thickness indicates whether the branch portion is stable (thick line) or unstable (thin line). The vertical dashed lines locate the value of the minimal threshold mouth pressure of each curve.