  We systematically study the nonequilibirum Kondo mechanisms of quantum noise
spectrum based on the accurate dissipaton--equation--of--motion evaluations. By
comparing the noise spectra between the equilibrium and nonequilibrium cases
and between the non-Kondo and Kondo regimes, we identify the nonequilibrium
Kondo features in the current noise spectrum, appearing in the region of
$\omega\in [-eV, eV]$. The Kondo characteristic at $\omega=\pm eV=\pm (\mu_{\rm
L}-\mu_{\rm R})$ display asymmetrical upturns and remarkable peaks in
$S(\omega)$ and $dS(\omega)/d\omega$, respectively. These features are
originated from the Rabi interference of the transport current dynamics, with
the Kondo oscillation frequency of $|eV|$. The minor but very distinguishable
inflections, crossing over $\omega=-eV$ to $\omega=+eV$, would be related to a
sort of Kondo-Fano interference between two Kondo resonances channels.
