  Recent vibration experiments in microgravity are re-examined. We show that
they demonstrate that "granular-gas" state exists only in the Knudsen regime,
that its excitation is "supersonic" and that the probability density function
of the pressure of the gas scales as (Af) to the power 3/2, with A and f being
the excitation amplitude and frequency. This paper pursues the description of
the experimental results. Then, it compares these ones to what can be predicted
from few simple modelling, which are (i) the classical-gas theory and (ii) the
thermodynamics of a single particle in a 1d box. The anomalous scaling of
pressure fluctuations (Af) to the 3/2 is explained by the crossover from the
regime of a single collision during the sampling time, which imposes p scales
as_ (Af) at small speed, to a multiple collision imposing p scales as_(Af)_ .
Air effect and effect of g-jitter are discussed and quantified. Influence of
grain-grain collisions is described on the distribution of speed. Pacs # : 5.40
; 45.70 ; 62.20 ; 83.70.Fn
