  Models of spontaneous wave function collapse describe the
quantum-to-classical transition by assuming a progressive breakdown of the
superposition principle when the mass of the system increases, providing a
well-defined phenomenology in terms of a non-linearly and stochastically
modified Schrodinger equation, which can be tested experimentally. The most
popular of such models is the Continuous Spontaneous Localization (CSL) model:
in its original version, the collapse is driven by a white noise, and more
recently, generalizations in terms of colored noises, which are more realistic,
have been formulated. We will analyze how current non-interferometric tests
bound the model, depending on the spectrum of the noise. We will find that low
frequency purely mechanical experiments provide the most stable and strongest
bounds.
