Abstract : In various audio signal processing applications, such as source separation and dereverberation, accurate mathematical modeling of both source signals and room reverberation is needed to properly describe the audio data. In a previous paper, we introduced a stochastic room impulse response model based on the image source principle, and we proposed an expectation-maximization algorithm that was able to efficiently estimate the model parameters in various experimental settings. This paper aims to extend the model in order to account for the dependency of the exponential decay over frequency, due to the walls usually absorbing less energy at low frequencies than at high frequencies. Our experimental results show that this refinement of the model is able to generate realistic room impulse responses, that are perceptively very close to the original ones.