  We investigate the features of the non-corrected thermal (non-thermal)
spectrum and the quantum corrected thermal (non-thermal) spectrum. We find
that: (i) using the quantum corrected non-thermal spectra, the black hole
radiation as tunneling is an entropy conservation process, and thus black hole
evaporation process is unitary; (ii) there are no obvious differences between
all spectra except for near the Planck mass scale by comparing their average
emission energies, average numbers of emissions and average emission energy
fluctuations; (iii) the energy covariances of Hawking radiations for all the
thermal spectra are exactly zero, while they are nontrivial for all the
non-thermal spectra. Especially, there are distinctly different maximums of
energy covariances for the temperature-corrected and energy-corrected
non-thermal spectra. Consequently, these differences provide a possible way
towards experimentally analyzing whether the radiation spectrum of black hole
is thermal or non-thermal with or without high order quantum corrections.
