The reverberation time was tested in a reverberation chamber with three acoustic absorbent materials commonly used in construction. The tests were performed with different materials, setups, and back air layers. Results have been compared with those where this material is placed as a single piece. Analyzing obtained data, a linear regression model is established to predict, for certain frequencies, the alteration produced in the reverberation time. So, knowing the absorption coefficient of an amount of material, it is possible to predict the different absorption coefficients placing the same material in separated pieces and different distances from room walls. The model has been validated and tested, which demonstrates its accuracy, it has also been proved to be applicable to a wide variety of materials. It becomes a simple predictive tool that allows to estimate in situ the alteration in the reverberation time due to the separation of the absorbent material in patches.