A complete set of vibrational spectra of ice XI, proton-ordered phase of ice Ih, has been obtained by molecular dynamics simulations using the Kumagai, Kawamura, and Yokokawa (KKY) potential model which allows unconstrained atomic motions. A remarkable difference between the power spectra of ice Ih and of ice XI was found in the librational band. In ice XI four major librational peaks were observed and assigned to three librational modes: wag, twist, and rock, whereas ice Ih is well known to have a broad librational band. Moreover, characteristic spectral properties, due to the ferroelectric structure of ice XI, were observed in the polarized power spectra of the atom velocities along the crystal axes.