Speaker comfort and increase of voice level in lecture rooms

Teachers often suffer health problems or tension related to their voice. These problems may be related to there working environment, including room acoustics of the lecture rooms which forces them to stress their voices. The present paper describes a first effort in finding relationships between the objectively measurable parameters of the rooms and the objective voice power produced by speakers.

In rooms with different sizes, reverberation time and other physical attributes, the sound power levels produced by six speakers where measured while giving a short lecture. Relevant room acoustic parameters were also measured in the rooms and subjective impressions from about 20 persons who had experience talking in these rooms were collected as well.

Analysis of the data revealed significant differences in the sound power produced by the speaker in the different rooms. It was also found that these changes were mainly related to the size of the room and to the gain or support produced by the room. To describe this quality, a new room acoustic quantity called 'room gain' is proposed.