  Inflation with Weyl scaling symmetry provides a viable scenario that can
generate both the nearly scaling invariant primordial density fluctuation and a
dark matter candidate. Here we point out that, in additional to the primordial
gravitational waves (GWs) from quantum fluctuations, the production of
high-frequency GWs from preheating in such inflation models can provide an
another probe of the inflationary dynamics. We conduct both linear analytical
analysis and nonlinear numerical lattice simulation in a typical model. We find
that significant stochastic GWs can be produced and the frequency band is
located around $10^8$ Hz $\sim$ $10^9$ Hz, which might be probed by future
resonance-cavity experiments.
