Objective Assessment of Speech Intelligibility in Small and Medium-Sized Classrooms

In this paper, experimental evaluation of speech intelligibility in small (177 m
³
) and medium-sized (270 m
³
) classrooms is presented. These studies are based on the assumption that the harmful effect of noise is negligible compared to that for reverberation. Speech intelligibility was computed from pre-measured room impulse response by a modulation and formant-modulation methods. It is shown that the speech intelligibility in a room significantly depends not only on the distance of the listener to the speaker, but also on the distance from reflective surfaces (walls), as well as on the orientation of the listener's head relative to these surfaces. In particular, it was found that the speech intelligibility was significantly higher at the distance of 30-50 cm from the rear wall than in the middle of the room in both studied rooms. At the same time, speech intelligibility at the distance of 1-2 m from any sidewall was lower than that near the rear wall. Moreover, for places near sidewalls, speech intelligibility was lower for the ear closer to a wall.