Our speaking voice is a wonderful expressive instrument. However, it can repel listeners if we fall into bad habits, for example, the monotone voice, speaking too fast, speaking too slow etc.
Your voice should be conversational in tone, similar to when you are speaking to a friend. Listen to a recording of your voice when delivering a speech. It may surprise you at first. Listen out for the speed, pitch, tone of your delivery. If you observe an issue, a great way to overcome this is by reading aloud and working on the issue, e.g. if you speak too fast read slowly.
I hope you've enjoyed this series of public speaking techniques and will use some them to improve your own performance.