General:
* Lecturer: A person who gives a formal talk on a specific subject.
* Presenter: A person who presents information, often with visuals.
* Orator: A skilled and eloquent speaker.
* Public speaker: A person who addresses an audience.
* Keynote speaker: A prominent speaker who gives a main address at an event.
* Guest speaker: A person invited to speak at an event.
* Speaker: A person who talks at an event.
* Talker: A person who enjoys speaking.
* Voice: A person who speaks for someone else.
Technical:
* Loudspeaker: A device that converts electrical signals into sound waves.
* Sound system: A system that amplifies and distributes sound.
* Microphone: A device that captures sound and converts it into electrical signals.
* Transducer: A device that converts one form of energy into another.
Informal:
* Chatterbox: A person who talks a lot.
* Gabber: A person who talks excessively.
* Mouthpiece: A person who speaks on behalf of someone else.
The best term to use will depend on the specific situation and the speaker's role.