BB spectra of 70 GHz (left) and 100 GHz (right) half-ring half difference noise maps, for both FFP8 simulations (green) and flight data (black). Differences at the low-ℓ end are caused by sample variance. These are pseudo-spectra, computed on 75% of the sky with the Galactic plane and point sources masked. Top: linear horizontal axis to show small-scale behaviour. Bottom: logarithmic horizontal axis to show large-scale behaviour.