  We explain how the Harish-Chandra Plancherel Theorem and results in relative
Lie algebra cohomology can be used in order to compute in a uniform way the
$L^2$-Betti numbers, the Novikov-Shubin invariants, and the $L^2$-torsion of
compact locally symmetric spaces thus completing results previously obtained by
Borel, Lott, Mathai, Hess and Schick. It turns out that the behaviour of these
invariants is essentially determined by the fundamental rank of the group of
isometries of the corresponding globally symmetric space. In particular, we
show the nonvanishing of the $L^2$-torsion whenever the fundamental rank is
equal to 1.
