Lecture hall differ from seminar room in that it allow for little versatility in use, although it is on less flexible than, for example, chemistry laboratories. Experimentation, group work, and other contemporary educational methods are not practicable in a lecture hall. On the other hand, lecture hall is excellent for focusing the attention of a large group on a single point, either an instructor or an audio-visual presentation, and modern lecture hall often feature audio-visual equipment. A microphone and loudspeakers are common to help the lecturer be heard, and projection screens may be used for large displays. The acoustic property of lecture hall has been the subject of numerous international studies, some even antedating the use of electronic amplification.