Seriously though, making convincing professional sounding 'voicoevers' is a specialised art. Which is why those who are lucky enough to have the right kind of voice - and know how to use it - can make a living doing it. See here for example: http://www.voiceovers.co.uk/
It's not that easy to do it well yourself.....
What kind of announcer? The talkies have been around for a long time. What period and what playback system are you trying to create? e.g. A sports announcer in a 1930s talking over a tannoy? Can you give an example?
In Sony Vegas 10, is there any way, to get an announcer's voice? Or to make my voice sound like an announcer? Like in the movies?.....
Taking a voice and manipulating it to sound like something in particular, like a tanoy, or a phone or something else is a case of using audio effects. Usually you can get most (or all) of the way using compressors and graphic equalisers. I'm not a vegas user, but I have no doubt that vegas includes those.
Other effects may help too, a little reverb if you're looking to sound like you're announcing to a large hall for instance.
It's a trial and error thing because everyone's voice is different. There's unlikely to be a one click solution, but by playing around with different combinations it shouldn't be too hard to get there.