  It is known that an acoustic wave incident on an infinite array of aligned
rectangular blocks of a different acoustic material exhibits total transmission
if certain conditions are met [1] which relate the unique "intromission" angle
of incidence with geometric and material properties of the slab. This
extraordinary acoustic transmission phenomenon holds for any slab thickness,
making it analogous to a Brewster effect in optics, and is independent of
frequency as long as the slab microstructure is sub-wavelength in the
length-wise direction. Here we show that the enhanced transmission effect is
obtained in a slab with grating elements oriented obliquely to the slab normal.
The dependence of the intromission angle $\theta_i$ is given explicitly in
terms of the orientation angle. Total transmission is achieved at incidence
angles $\pm \theta_i$, with a relative phase shift between the transmitted
amplitudes of the $+\theta_i$ and $- \theta_i$ cases. These effects are shown
to follow from explicit formulas for the transmission coefficient. In the case
of grating elements that are rigid the results have direct physical
interpretation. The analytical findings are illustrated with full wave
simulations.
