  In microfluidic applications involving high-frequency acoustic waves over a
solid boundary, the Stokes boundary-layer thickness $\delta$ is so small that
some non-negligible slip may occur at the fluid-solid interface. This paper
assesses the impact of the slip by revisiting the classical problem of steady
acoustic streaming over a flat boundary with the Navier boundary condition
$u|_{y=0} = L_\mathrm{s} \partial_y u|_{y=0}$, where $u$ is the velocity
tangent to the boundary $y=0$, and the parameter $L_\mathrm{s}$ is the slip
length. The limit outside the boundary layer provide an effective slip
velocity. A general expression is obtained for the streaming velocity outside
the boundary layer as a function of the dimensionless parameter
$L_\mathrm{s}/\delta$. Particularising to travelling and standing waves shows
that the boundary slip respectively increases and decreases the streaming
velocity.
