Speech Directivity. (Speaker and Listener Orientation)
orientation can be an important factor in classrooms and meeting rooms
in particular. As indicated in the diagram, there is a difference of about
10 decibels (dBA) in speech levels between the front and back of the speaker.
This amounts to about 1-1/2 decibels per 30 degrees of rotation from the
head on direction of the speech signal.
The average sound level of a male speaker is about 65-64 decibels at a distance of 3 feet from the speaker. The average speech level of a female speaker is about 2-4 decibels lower at a 3-foot distance from the speaker.
Orientation of the speaker to the listener is an important consideration. This is particularly so when considered in context of the Inverse Square Law, which teaches us, that for every doubling of the distance the signal will diminish in intensity by approximately 6 decibels.