= Graphical corner frequency of a Lorentzian spectrum
{title2=$f_c=\sqrt{C/P_0}$}
For <power spectral density> $P(f)=C/(f^2+f_c^2)$, the low-frequency plateau is $P_0=C/f_c^2$ and the high-frequency asymptote is $C/f^2$. Their intersection on a <log-log plot> gives the displayed corner <frequency>. Equivalently $P(f_c)=P_0/2$. Use the range unaffected by additional low-frequency <noise> or high-frequency filtering; a measurement chain can otherwise shift an apparent corner.
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