Amplitude per radial mode as a function of T_eff for ϵ Indi and a number of cool dwarfs with published measurements. Reported statistical uncertainties for the mode amplitudes are comparable in size to the plotted symbols. Data points are colour-coded according to the corresponding ratio. Except for ϵ Indi (see Appendix C) and the Sun (Mamajek & Hillenbrand 2008), all measurements are from Gomes da Silva et al. (2021). Two scalings of the mode amplitudes are shown, differing in terms of the exponent s (s = 0.7, dotted curve; s = 1.5, solid curve). The adopted L/M relation is from stellar models in a 4.57 Gyr, solar-metallicity isochrone computed with the PAdova and TRieste Stellar Evolution Code (PARSEC; Bressan et al. 2012).