Increase sound volume above 150% without loosing synchronization

Question

I would like to increase the sound volume substantially above 150%. There have been some suggestions to this topic (extract sound and work with sound studio or audacity).
When I do this I loose synchronization of audio and video. Does anyone know a way to increase sound substantially without loosing synchronization?
Bertrand Völckers
iMac   Mac OS X (10.4.7)  

Answer 1

It doesn't necessarily produce any distortion ..it all depends on how loud - or quiet - the sound was to start with.
In Audacity & Sound Studio you can see if there's going to be any distortion as you raise the sound level: if the tops & bottoms of the visible waveform get chopped off ("clipped", in techno-speak) as the waveform grows larger, then you'll hear distortion.
If there's no clipping, and the waveforms keep their original shape - but just become larger - then there'll be no distortion ..bigger doesn't necessarily mean distorted, unmanageable or unbearable.
It's not necessarily VERY LOUD EITHER! ..If the original audio was just the hum of air through a swan's wings as it flew by, that might be almost inaudible on your sound track. By raising the audio level, say, 500% it may become noticeable.
That'd also raise the level of everything else by 500%, too, but if it was a still day, that might be just a slight background hiss. You could filter out the general hiss, and just leave the thrum of the swan flying by..
In this bit of audio..
..raising the levels by 500% would certainly distort (by clipping; chopping off the edges) the loudest regions, but the quietest sections are unlikely to become distorted.
If all the sound is as low as the quiet sections above, then there's unlikely to be any distortion after boosting it.