Anyone know how to get rid of an echo made by an empty room in FCP?

You can't.

An echo is the reflection of the sound waves of your actor's voice slightly behind the waves coming out of your actor's mouth.

So since they are pretty much the same sound waves as your actor's voice, if you take out the echo, you take out the actor's voice as well.

That sucks, ok thanks.

I bet its possible to write an algorithm that can detect and remove an echo. But its certainly not within the realm of possibility for an FCP plugin.

yeah, I tried to do that once with no success, too bad FCP doesn't have an anti-reverb filter

What about in premiere or after effects?

hoestly, you really can't. not even on an audio editing program like ProTools with the full set of plug ins.

it's not about the program, it's about the physics of sound. once echo is recorded, that's it, it's there. echo is different than an annoying noise, since the noise is at a different frequency than the sound you want to bring out. echos are at the exact same frequency, so anything you do the echo you do to the original sound.

Video editing programs aren't the best to deal with audio issues like these. They can do quite a bit, but you have see that most of the sound plug-ins for video editing programs is either to do something very quickly, or to approximate what the director has in mind. All the audio is still edited, processed, and mixed on an audio program, because they are built to handle a lot more audio issues than a video editing program.