The noise covariance matrix is useful for SNR and g-map computation and, with the noise correlation matrix, commonly taken as metrics to characterize decoupling of denser and denser receive arrays. Roemer provided a resistance matrix accounting for noise correlation. In the literature, Bosma defined the noise covariance matrix from the scattering matrix, easing predictions based on electromagnetic simulations or VNA measurements. Here noise correlation is analyzed for 50 Ω power-matched and low-input impedance preamplifiers. As predicted by Bosma, strong coupling does not necessarily imply a high noise correlation, which also depends on the ports impedance matching.