  Here we present a detailed study of the broadband noise in the power density
spectra of the black hole X-ray binary MAXI J1820+070 during the hard state of
its 2018 outburst, using the Hard X-ray Modulation Telescope (Insight-HXMT)
observations. The broadband noise shows two main humps, which might separately
correspond to variability from a variable disk and two Comptonization regions.
We fitted the two humps with multiple Lorentzian functions and studied the
energy-dependent properties of each component up to 100--150 keV and their
evolution with spectral changes. The lowest frequency component is considered
as the sub-harmonic of QPO component and shows different energy dependence
compared with other broadband noise components. We found that although the
fractional rms of all the broadband noise components mainly decrease with
energy, their rms spectra are different in shape. Above $\sim$ 20--30 keV, the
characteristic frequencies of these components increase sharply with energy,
meaning that the high-energy component is more variable on short timescales.
Our results suggest that the hot inner flow in MAXI J1820+070 is likely to be
inhomogeneous. We propose a geometry with a truncated accretion disk, two
Comptonization regions.
