  The spin wave excitations of the geometrically frustrated triangular lattice
antiferromagnet (TLA) $\rm CuFeO_2$ have been measured using high resolution
inelastic neutron scattering. Antiferromagnetic interactions up to third
nearest neighbors in the ab plane (J_1, J_2, J_3, with $J_2/J_1 \approx 0.44$
and $J_3/J_1 \approx 0.57$), as well as out-of-plane coupling (J_z, with
$J_z/J_1 \approx 0.29$) are required to describe the spin wave dispersion
relations, indicating a three dimensional character of the magnetic
interactions. Two energy dips in the spin wave dispersion occur at the
incommensurate wavevectors associated with multiferroic phase, and can be
interpreted as dynamic precursors to the magnetoelectric behavior in this
system.
