Bifurcation diagrams representing the evolution of root mean square value of the downstream pressure p with respect to the mouth pressure p_m, for the lip parameters of Table 1 and two different values of the lip frequency: F_ℓ = 101.8 Hz (blue curve) and F_ℓ = 93.2 Hz (green curves). Stable and unstable parts of the branches are represented by solid and dashed lines, respectively. The pressure threshold is indicated in each case by a red circle.