Have you ever been to presentation where the presenter spoke in a monotone, “It’s- great-to-see-everybody-Thank-you-very-much-for-coming-today-I-have-some-exciting-news-for-you.” BOOOORING!
You want to increase your volume, and increase your voice inflection, which means the variance in the pitch or the tone of your voice. It is more interesting, more exciting to listen to a presenter that has passion and feeling in their voice. Speak to your audience with belief and you will soon see they will share that belief.
The best way to practice this is by reading a book aloud to someone else and then getting them to give you feedback. If you have children it gives a whole new meaning to a bedtime story. Remember the best speakers are great storytellers.