Comparison of noise estimates at high multipoles, as a ratio of the full noise level and the white noise level (blue). The green dots show the estimate from half-ring maps. The orange dots show the mean of 10 000 Monte Carlo simulations. The error bars here include the statistical variation only. The values shown are mean values of the noise spectrum in the range ℓ = 1150−1800. The absolute white noise levels in μK² are reported in the last two columns of Table 7.