How we project our voice to the audience is an essential aspect of acting. Here is some advice on the subject from Italian actor Dario Fo, 1997 Nobel Prize for Literature. There are certainly many diverse voice techniques used by different schools of acting. However, in "The Tricks of the Trade" Fo generously explains his ideas, based on his own vast acting experience:
"The most important thing is to learn to project the voice, to articulate and form words in the most intelligible way possible. The organ on which one has to push so as to produce crisp resonance is the abdomen. It is essential to stretch the solar plexus like a drum skin, and to undertake expercises to achieve this aim, so that sounds of the lowest possible tonality can be obtained. Acting with the chest voice or from the abdomen prevents the voice from going hoarse, because the vocal chords, which are a matching pair, produce a series of shorter, slower vibrations when creating deep tones and the reist of the so-called abrasive whip-effect (when the two rub one against the other, with disastrous consequences) is avoided. In addition, the lower tones of voice make a bigger impact on the listener. It is a common mistake to believe that raising the pitch or going into falsetto helps projection, when exactly the opposite is the case. Pressure on the abdomen with the emission of deeper sounds is the most effective means of throwing the voice furthest."
Fo also give some ideas concerning technique:
"The key to success lies in letting the breath out very slowly, without undue pressure; in other words, no more than is needed to project the voice the required distance. Never believe that an almighty release of breath is required for an expression of great vocal power. This is one of the most common mistakes of amateur dramatic societies. Resonance is determined principally by the pressure that is brought to bear on the abdomen and on all the muscles of the vocal apparatus, that is, the muscles of the oesophagus, of the glottis and the epiglottis as well as those of the velum, the back-palatal zone."
"It is control and not the quantity of air expelled, that determines power and produces efficient voice projection. Another essential trick of the trade is the method that allow the talker to take in rapid gulps of air while talking, without having to stop to open his mouth. To be more precise, I should correct the expression I have just used. Rather than a trick of the trade, it is a technique that must be acquired by practice, an exercise involving the use of the nose (assuming it is not blocked by a cold). It is important to use this technique sparingly, and often it will be better to breathe quite naturally, drawing attention to the fact rather than attempting to disguise it."