  We consider a point-like observer that moves in a medium illuminated by noise
sources with Lorentz-invariant spectrum. We show that the autocorrelation
function of the signal recorded by the observer allows it to perceive its
environment. More precisely, we consider an observer with constant acceleration
(along a Rindler trajectory) and we exploit the recent work on the emergence of
the Green's function from the cross correlation of signals transmitted by noise
sources. First we recover the result that the signal recorded by the observer
has a constant Wigner transform, i.e. a constant local spectrum, when the
medium is homogeneous (this is the classical analogue of the Unruh effect). We
complete that result by showing that the Rindler trajectory is the only
straight-line trajectory that satisfies this property. We also show that, in
the presence of an obstacle in the form of an infinite perfect mirror, the
Wigner transform is perturbed when the observer comes into the neighborhood of
the obstacle. The perturbation makes it possible for the observer to determine
its position relative to the obstacle once the entire trajectory has been
traversed.
