Compress, normalize, amplify -- differences ?

[Robert W. Mantha]

All three can be used to adjust volume in one or more tracks -- I've been scanning pretty well everything that has been written on these functions; could someone just briefly explain the essential differences between the three (or else why have them?) and when we would use one or the other, or all three, and if so, in what logical sequence should we use them?

I understand that the ultimate objective is to bring the relative volumes of recording segments within a pleasing, natural range of one another, all the while compensating for the differences which are due to different recording volumes (gain) at different points in time. Thanks ! RWM

[richardash1981]

Compression applies a gain that varies according to the audio signal level within the audio track.
Normalise applies a fixed gain within the audio track, which is calculated to raise the peak level to the maximum possible without clipping.
Amplify provides a user-chosen amount of fixed gain to the track.

[kozikowski]

<<<I understand that the ultimate objective is to bring the relative volumes of recording segments within a pleasing, natural range of one another, all the while compensating for the differences which are due to different recording volumes (gain) at different points in time.>>>

That's what everybody wants them to do, but only the compressor approaches actually doing that--usually badly.

There's nothing like preparing all your music selections ahead of time. Once they're part of a mix, it's really difficult to "level out the field" and make everything sound the same.

As above, the volume control is just that. Adjust once at the top of the show and that's it. The whole performance gets louder or softer the same amount from where it started.

Normalize is automatic volume control. Adjust the whole performance up or down once paying attention to the one worst peak volume.

Compressors do take the volume of the performance into account and skillfully adjusted can "level out" a performance. Books have been written about how to effectively do that. Attack, Release, Delay, and Ratio. Most compressors have all four of those adjustments and some more. The adjustments change a lot depending on the type of music in the performance and whether or not somebody speaks. The compressors in an AM radio station can be radically different from FM. Different Talk from Rock.

It's not unusual to spend more time patching the settings in a compressor than it would have taken to just go back and prepare the original music clips in the first place. You might be able to short cut the process by "normalizing" all the individual cuts before the final edit. That's a lot easier than adjusting by hand and will get you into the ballpark quickly.

Audacity doesn't have the best tools for locating the beginning and end points of a long clip inside a big mix, so again, doing it in post production will drive you nuts.

Have a good time.

Koz

[kozikowski]

I am reminded there is a way to make this process very slightly less painful (but still manual) and that's the Envelope tool.

I can't find the wiki for it, but just under half-way down this page is a description of it:

http://www.transom.org/tools/editing_mi ... acity.html

Koz