I've tried to use the speakerphone while calling people in noisy environment.
And it works! You just have to lower the speaker volume, turn back the phone and put the speakerphone to your ear.

The only problem is that the mic sensitivity is boosted and people on the other end of the line are complaining about ambient sound or hearing themselves.

I tried Freedom to reduce mic sensitivity but it doesn't seem to work (not designed to do it while on call). I know it is possible to modify the mic sensivity (SoundRec does it well) but I don't know any apps that will enable it while on call...

Any idea, dear Treo users ?