  Primordial black holes (PBHs) can form as a result of primordial scalar
perturbations at small scales. This PBH formation scenario has associated
gravitational wave (GW) signatures from second-order GWs induced by the
primordial curvature perturbation, and from GWs produced during an early PBH
dominated era. We investigate the ability of next generation GW experiments,
including BBO, LISA, and CE, to probe this PBH formation scenario in a wide
mass range. Measuring the stochastic GW background with GW observatories can
constrain the allowed parameter space of PBHs for masses 1e9 - 1e27 g. We also
discuss possible GW sources from an unconstrained region where light PBHs (<
1e9 g) temporarily dominate the energy density of the universe before
evaporating. We show how PBH formation impacts the reach of GW observatories to
the primordial power spectrum and provide constraints implied by existing PBH
bounds.
