  We consider the influence of potential quark matter existing at high
densities in neutron star interiors on gravitational waves (GW) emitted in a
binary neutron star merger event. Two types of equations of state (EoS) at zero
temperatures are used, one describing pure nuclear matter, the other nuclear
matter with a phase transition to quark matter at very high densities. Binary
equilibrium sequences close to the innermost stable circular orbit (ISCO) are
calculated to determine the GW frequencies just before merger. It is found that
EoS effects begin to play a role for gravitational masses larger than
$M_\infty\simeq1.5M_\odot$. The difference in the gravitational wave frequency
at the ISCO grows to up to $\simeq 10%$ for the maximal allowed mass given by
the EoSs used. Then, we perform 3D hydrodynamic simulations for each EoS
varying the initial mass and determine the characteristic GW frequencies of the
merger remnants. The implications of quark matter show up mainly in a different
collapse behaviour of the merger remnant. If the collapse does not take place
immediately after merger, we find a phase difference between two EoS's in the
post-merger GW signal. We also compare the GW frequencies emitted by the merger
remnant to values from simulations using a polytropic EoS and find an imprint
of the non-constant adiabatic index of our EoSs. All calculations are based on
the conformally flat (CF) approximation to general relativity and the GW signal
from the merger simulation is extracted up to quadrupole order.
