A new derivation for the reverberation time equation is here proposed. From the accurate analysis of a model describing the acoustics of enclosed spaces in terms of a feedback system, a surprisingly easy and deep insight of the complex phenomenon of reverberation is readily obtained without any loss of formal rigor. While the experimental consistency of the approach is pointed out by directly measuring the average absorption coefficient of the room, its theoretical consistency follows from the ability of the model to deduce the well-known Norris-Eyring formula for the reverberation time. Finally, starting from a new definition of reverberation time considering the phenomenon of reverberation essentially connected with the whole history of the sound field and not only with its transient parts (buildup or decay), a new equation for reverberation time is obtained.