Incoherent inelastic neutron scattering experiments have been performed in order to establish the longitudinal acoustic modes (LAM) in orthorhombicn‐C32H66crystals by a method different from Raman scattering. Besides the Raman active first order of LAM, the second order of LAM, which is Raman inactive, has been observed. No dispersion of the LAM’s was to be seen. It is masked completely by effects resulting from the absence of optical selection rules. In addition to the LAM’s, the antiparallel translational mode in chain direction, which is optical inactive, was identified. Its assignment was confirmed from theQdependence of the scattering intensity.