  Using the well-known Olami-Feder-Christensen model as our paradigm, we show
how to modify uniform driven self-organized critical models to generate
$1/f^\alpha$ noise. Our model can reproduce all the main features of
$1/f^\alpha$ noise: (1) $\alpha$ is close to one and does not depend on the
dimension of the system. (2) The $1/f^\alpha$ behavior is found for very low
frequencies. (3) The spatial correlations do not obey a power law. That proves
that spatially extended systems based on activation-deactivation processes do
not have to be point-driven to produce $1/f^\alpha$ noise. The essential
ingredient is a local memory of the activation-deactivation process.
