Due to the nonlinear interaction between the ultrasonic waves emitted by the parametric loudspeaker, a directional sound beam is generated along with harmonic distortion. It is known that the single sideband amplitude modulation (SSB-AM) technique is one of the most effective ways of reducing the harmonics. A 3rd-order inverse Volterra filter (VF) is designed on the basis of the SSB-AM in this paper to further compensate the nonlinearities of the parametric loudspeaker. Meanwhile, the diagonal Volterra filter (DVF) with the advantage of lower complexity compared to the conventional VF is also proposed. The experimental results demonstrate that the inverse DVF is able to reduce the harmonic distortion to meet high fidelity requirement nearly the same as the inverse VF while requiring less computational resources.