The All About Symbian podcast is put together by AAS staff in various parts of the world sharing a conference call over Skype. You don't need brilliant sound quality, but you do need a voice that people are willing to listen to for 10 - 30 minutes.
You can train your voice if you're not happy with it, just record yourself and try out different speaking styles until you settle on something that works for you. You can usually see the current sound level on most recording software, and you can use this level to help you aim for a steady volume.