In the classroom, students are daily exposed to multiple factors that combine to create adverse conditions for listening to and understanding what the teacher is saying. These conditions increase the listeners’ effort to understand and learn. One of these adverse conditions is the teacher’s voice and communication both affected by the room acoustics and other environmental factors. The concept of “speakers’ comfort” describes the interplay between the speaker, the speaker’s perceptions of the support from the room, of getting the message across to the listeners, and from the vocal apparatus, without having to overload and strain voice and speech. Despite the ubiquity of these conditions, there is little knowledge concerning the way in which factors combine to influence listening comprehension and how to decrease the effort of listening and increase the speaker’s comfort. This presentation will cover a sequence of studies of 245 eight-year-old children. Their language comprehension was tested at different levels, tests presented by typical and dysphonic teacher voices. The presentation will also include results from two intervention studies aiming to increase teachers’ awareness of the adverse listener/speaker conditions in the classroom and to give them tools to decrease the effort of the listener and the speaker.