This work presents an analysis of distant-talking speech recognition in a variety of reverberant conditions, correlating ASR performance to the acoustic characteristics of a given propagation channel. In particular we show how, for a digit recognition task, the ASR accuracy is directly related to the Early-to-Late Reverberation ratio of the room impulse response, capturing in a single parameter the reverberation properties of a given channel independently of the setup. Consequently, this measure can be successfully considered for acoustic model training either selecting the most suitable model for a given spatial configuration, or defining the subset of RIRs to be used for the creation of multi-condition models. Experimental results on simulated data as well as on data generated with real impulse responses support our claims.