Dereverberation is an important preprocessing step in many
speech systems, both for human and machine listening. In
many situations, including robot audition, the sound sources
of interest can be incident from any direction. In such circumstances,
a spherical microphone array allows direction of arrival
estimation which is free of spatial aliasing and directionindependent
beam patterns can be formed. This contribution
formulates the Weighted Prediction Error algorithm in the
spherical harmonic domain and compares the performance to
a space domain implementation. Simulation results demonstrate
that performing dereverberation in the spherical harmonic
domain allows many more microphones to be used
without increasing the computational cost. The benefit of
using many microphones is particularly apparent at low signal
to noise ratios, where for the conditions tested up to 71%
improvement in speech-to-reverberation modulation ratio was
achieved.