Can You Hear Me Now?
Use the microphone. Ask the audience if they can hear you. And then read their body language.
So many times, I hear a (usually male) presenter say, "I've got a strong voice, so I'm not going to use the microphone."
And for the first minute, he starts out strong, and we all can hear him. Then, he goes into his normal voice range, and some audience members can't hear, so they start to fidget. The presenter prattles on, oblivious to audience discomfort at interrupting him, or telling him to speak up.
Even if you have a strong voice, don't be mike shy! Put it on and ask the audience if they can hear you. At the very least, you've set the tone for a more interactive presentation by asking the audience a question and getting them involved.
And remember don't read your speech or presentation:
read your audience. Their very body language should let you know how you sound to them.