The use of spherical microphone arrays (SMA) for room acoustic analysis has been widely studied in recent literature. Research has mainly focused on source localization and the extraction of room acoustic parameters from measured directional room impulse responses (DRIR). In practice, DRIRs are typically corrupted by measurement noise, which limits their use for 3-D reverberation processing and auralization. Due to the exponential energy decay, the noise floor masks especially the late part of the DRIR. In this paper we present a method for improving the signal-to-noise ratio (SNR) of measured impulse responses. This method is based on a statistical space-time-frequency model of the late reverberation decay. It first estimates the spatiotemporal energy decay relief from measured DRIRs and then replaces the corrupted part of the DRIR by a modelled diffuse sound field We applied this method to DRIRs measured in IRCAM’s variable acoustics concert hall and discuss the results.