There does not need to be any confusion about when you should use a microphone. Just remember the “Rule of 40” and you will not only be safe, but effective as well.

Whenever there are more than 40 people in a room of any size, use a microphone.

If you have an audience of less than 40, you still might want amplification if:

1. Your voice projection is soft.
2. The room is large and acoustically poor.
3. You want to use special vocal effects such as whispers, dialects or other dramatic devices often used by performers, humorists, and singers.
4. A stage presence adds to the impact of your talk.

And, if in doubt, remember: You’ll be safe and never sorry if you always use a mike.