The spin wave excitations of the geometrically frustrated triangular latticeantiferromagnet (TLA) $\rm CuFeO_2$ have been measured using high resolutioninelastic neutron scattering. Antiferromagnetic interactions up to thirdnearest 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 dispersionrelations, indicating a three dimensional character of the magneticinteractions. Two energy dips in the spin wave dispersion occur at theincommensurate wavevectors associated with multiferroic phase, and can beinterpreted as dynamic precursors to the magnetoelectric behavior in thissystem.
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