We consider the description of quantum
noise within the framework of the standard Copenhagen interpretation of
quantum mechanics applied to a composite system environment setting.
Averaging over the environmental degrees of freedom leads to a
stochastic quantum dynamics, described by equations complying with the
constraints arising from the statistical structure of quantum
mechanics. Simple examples are considered in the framework of open
system dynamics described within a master equation approach, pointing
in particular to the appearance of the phenomenon of decoherence and to
the
relevance of quantum correlation functions of the environment in the determination of the action of quantum noise.