I just got off a phone lesson with a wonderful sportscaster (Coach John Bunting- and no, that's not a pic of him, hehe). He has a great voice and great energy and has some fabulous gigs coming his way. We talked about many things but one I wanted to share with you is how to power the voice for public speaking... effectively and safely.
The answer is to use the power of resonation -- NOT of excessive breath pressure. This is of course the same thing we do with the singing voice. Resonation requires access to resonation zones... which means you need your breath vibrating your vocal cords just right and that vibration needs to be able to access all your resonation zones. To gain that access, the throat channel has to be open.
There is one more thing you need to be a powerful speaker. You need to know to whom you are talking, and what it is that you're trying to tell them. Purposing your voice to give a message to a specific target should automatically cause you to use communicative tone colors that do the job of delivering that message.
So to simplify... to speak with power requires breath POWER, a voice PATH through an open throat, and a PERFORMANCE that communicates. Sound familiar? PPP technique works with both singing and speaking voices. To check more deeply into this training, go to the PPP page on my website.