This work presents a perceptual model based on a complex IIR filterbank. The filterbank with a frequency resolution of 4 bands per Bark consists of 104 filters whose slopes are designed to take spectral masking effects into account. The filter outputs are used to obtain masking thresholds with the following post processing. To obtain resonable masking thresholds from the spreading outputs, a post masking stage is required. Here, we propose a comodulation dependent adaptation of the postmasking decay to model Comodulation Masking Release (CMR) effects. This approach explicitely considers the dip-listening effect known from literature. The final masking thresholds are obtained by weighting the postmasking outputs by a tonality dependent gain, controlled using spectral flatness estimation. A listening test compares the proposed method to an already known approach using direct CMR based modification of the masking threshold gains.