Comparison of the calculation results in the case of the zoom on NGC 2024 with three different methods of computing the power spectra: either the power spectra resulting from Fourier-transformed data are used directly, with a linear interpolation between the points (data only, blue), or the result of the power law fit at high frequencies is extrapolated to low frequencies to provide a power law throughout the whole range of frequencies (fit only, green), or a composite version of the power spectrum is built using the raw data at low frequencies, and the fit result at high frequencies (data + fit, red). The error bars account for the observational noise as well as for the g₂₁ uncertainty. The horizontal line marks the equipartition limit.