Variety:it is importabt for teacher to vary the quality of thrir voices-and the volume they speak at - depending on the tupe of lesson and the type of activity. So the kind of voice you use to give instructions or introduce a new activity will be different from the voice which is most appropriate for conversation or an informal exchange of view or information.
In one particular situation,teacher often use very loud voices,and that is when they want students to be quiet or stop doing something(see the next section )But it is worth pointing out that speaking quietly is often just as effective a way of getting the students' attention since,when they realise that you are talking,they will want to stop and listen in case you are saying something important or interesting.However,for teachets who almost never rise their voices,thr occssional shouted interjection may have an extremely dramatic effect,and this can sometimes be beneficial.