  We propose a physical model for the peaked noise in the X-ray power density
spectra of accreting X-ray binaries. We interpret its appearance as an
interference of two Comptonization continua: one coming from the up-scattering
of seed photons from the cold thin disk and the other fed by the synchrotron
emission of the hot flow. Variations of both X-ray components are caused by
fluctuations in mass accretion rate, but there is a delay between them
corresponding to the propagation timescale from the disk Comptonization radius
to the region of synchrotron Comptonization. If the disk and synchrotron
Comptonization are correlated, the humps in the power spectra are harmonically
related and the dips between them appear at frequencies related as odd numbers
1:3:5. If they are anti-correlated, the humps are related as 1:3:5, but the
dips are harmonically related. Similar structures are expected to be observed
in accreting neutron star binaries and supermassive black holes. The delay can
be easily recovered from the frequency of peaked noise and further used to
constrain the combination of the viscosity parameter and disk height-to-radius
ratio $\alpha (H/R)^2$ of the accretion flow. We model multi-peak power spectra
of black hole X-ray binaries GX 339$-$4 and XTE J1748$-$288 to constrain these
parameters.
