Top: Dispersion of the 150 On–Off random selections fluxes in the CO datacube of the region W43-MM2 for channels at velocities of 59.2 km s⁻¹ and 100.1 km s⁻¹. The mean (μ) and standard deviation (σ), which is assumed for the noise in a respective channel, are indicated in the panel. Middle: noise spectra of the CO datacube of the region W43-MM2 (in blue, left y-axis) overlaid with its mean cube spectra (in orange, right y-axis). The mean cube spectra is computed by averaging the fluxes of all the pixels (except those at the edges) at every channel. The green dotted line is centered on the V_LSR of the region. The two channels represented in the top panel are indicated with the red dashed lines. Bottom: same as above for the SiO datacube.