Which are the audio options?

You can join ProZ.com Webinar via VoIP (Mic & Speakers) or telephone. Your choice of audio mode is provided in the Audio pane of your Control Panel. See image attached.

By default, you will be joined into the Webinar muted.

Note that, if you choose to join via VoIP, you will need speakers to listen to the Webinar and a microphone to speak (if the organizer gives you speaking rights).