In the 20th century, many buildings were rebuilt, because they lost their usual functioning use. Actually, many of them have had an acoustic rehabilitation because they are used for music performances or for conferences. Architectural acoustics is considered an area in the acoustic science that deals with the control of noise within rooms and buildings. This subject tries to improve the auditory subjective perception inside these rooms. As Leo Beranek stated in some of his books, ?there is no easy road to an understanding of present-day acoustics?. First of all, we have to understand all the physical mechanisms and laws governing in such acoustic media and afterwards apply to a particular case. This is our purpose in this book. This work is oriented to be a case of study for practitioners, about the acoustic rehabilitation and design process and how to interpret the results in the process of room acoustic rehabilitation.