  We describe the dynamic response of a two-dimensional hexagonal packing of
uncompressed stainless steel spheres excited by localized impulsive loadings.
After the initial impact strikes the system, a characteristic wave structure
emerges and continuously decays as it propagates through the lattice. Using an
extension of the binary collision approximation (BCA) for one-dimensional
chains, we predict its decay rate, which compares well with numerical
simulations and experimental data. While the hexagonal lattice does not support
constant speed traveling waves, we provide scaling relations that characterize
the power law decay of the wave velocity. Lastly, we discuss the effects of
weak disorder on the directional amplitude decay rates.
