I have mentioned the components of an interesting voice but reading about them will not improve your delivery.
\ou need to practice. If you do not have the opportunity to practice your speaking in public as much as you would like, or if you prefer to do so outside your own working environment, consider joining a speaking club which offers you the possibility of learning to present your views in an interesting and persuasive manner. At most of them, the members come from a variety of backgrounds with the common purpose of practicing their speaking skills. Each speaker is assessed following his assignment, a prepared speech or spontaneous talk, say, so that he receives instant feedback on his performance to enable him to improve.
I advise my clients to read aloud. Try reading a book to your children, or read a passage from the newspaper into a tape recorder to learn how to add variety, color and drama to your voice. To be a convincing speaker, you need the magical quality of enthusiasm. Although it may be bubbling away inside you, if your voice doesn’t express it, your audience won’t be able to share it with you.