Spectrum of eleven-dimensional supergravity on a pp-wave background

We calculate the spectrum of the linearized supergravity around the maximally supersymmetric pp-wave background in eleven dimensions. The resulting spectrum agrees with that of zero-mode Hamiltonian of a supermembrane theory on the pp-wave background. We also discuss the connection with the Kaluza-Klein zero modes of an ${\mathrm{AdS}}_4\times {\mathrm{S}}^7$ background.