  Using a population synthesis approach, we compute the total merger rate in
the local Universe for double neutron stars, double black holes, and black hole
-- neutron star binaries. These compact binaries are the prime source
candidates for gravitational-wave detection by LIGO and VIRGO. We account for
mergers originating from field populations and from dense stellar clusters. For
both populations we use the same treatment of stellar evolution. Our results
indicate that the merger rates of double neutron stars and black hole --
neutron star binaries are strongly dominated by field populations, while
merging black hole binaries are formed much more effectively in dense stellar
clusters. The overall merger rate of double compact objects depends sensitively
on the (largely unknown) initial mass fraction contained in dense clusters
f_cl. For f_cl < 0.0001, the Advanced LIGO detection rate will be dominated by
field populations of double neutron star mergers, with a small but significant
number of detections ~20 yr^-1. However for a higher mass fraction in clusters,
f_cl > 0.001, the detection rate will be dominated by numerous mergers of
double black holes originating from dense clusters, and it will be considerably
higher, ~25 - 300 yr^-1. In addition, we show that, once mergers of double
black holes are detected, it is easy to differentiate between systems formed in
the field and in dense clusters, since the chirp mass distributions are
strikingly different. Finally, we point out that there may exist a population
of merging black hole binaries in intergalactic space.
