This article investigates the audibility and intelligibility of preaching in a loud voice inside the Cathedral Notre-Dame de Paris during the Middle Ages, after the construction of the Gothic cathedral, until the late 19th century. Through this time period, the locations where oration took place changed along with religious practices inside the cathedral. Here, we combine a historical approach with room acoustic modelling to evaluate the locations inside the cathedral where one would hear sermons well. In a reverberant cathedral such as Notre-Dame, speech would be most intelligible in areas near the orator. Until the introduction of electronically amplified public address systems, speech would not be intelligible throughout the entire cathedral.