  The CSL model predicts a progressive breakdown of the quantum superposition
principle, with a noise randomly driving the state of the system towards a
localized one, thus accounting for the emergence of a classical world within a
quantum framework. In the original model the noise is supposed to be white, but
since white noises do not exist in nature, it becomes relevant to identify some
of its spectral properties. Experimental data set an upper bound on its
frequencies, while in this paper we bound it from below. We do so in two ways:
by considering a 'minimal' measurement setup, requiring that the collapse is
completed within the measurement time; and in a measurement
modeling-independent way, by requiring that the fluctuations average to zero
before the measurement time.
