Profile of the modified Brunt–Väisälä and ℓ = 1 Lamb frequencies (thick solid and dashed lines, respectively) for two 1.2 M_⊙ red giant models with ν_max ≈ 200 μHz (blue) and ν_max ≈ 60 μHz (red). These both models correspond to stars at the beginning of the ascent of the RGB and at a point just before the luminosity bump, respectively. The usual Brunt–Väisälä and ℓ = 1 Lamb frequencies, N and S₁, are represented by the light thin solid and dashed lines, respectively. The vertical dash-dotted lines indicate the hydrogen-burning shell and the horizontal strip symbolizes a typical 6Δν-wide observed frequency range around ν_max, for each model with the corresponding color. The buoyancy and acoustic cavities for a mode of frequency ν are located where 2πν ≤ (𝒩 and 𝒮₁) and 2πν ≥ (𝒩 and 𝒮₁), respectively.