You could try using a Noise gate. Use the Threshold control on the Noise Gate to try an eliminate the low-level noise.
There are some very good noise-reduction plugins out there, like iZotope's RX plugin:
What type of warping do you want to do to the voices? Stretching then, pitching them.....
Do you have Melodyne? This is an excellent plugin to get these results. We also have some excellent tutorials on Melodyne, on how to change and manipulate audio:
Or you can use the Transpose and Detune functions in Ableton to pitch the audio up or down, and try the warping in Ableton to stretch the audio.
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