[wplug] Audio: Compression Utility?

[bgtrio at yahoo.com]

Robert, 

Pretty much every song you hear on the Radio is heavily compressed to give 
it a "loud" feeling.  Here's a nice explanation I found after a quick 
googling:

"So what exactly is normalization, as opposed to compression, and how do 
they interact? Let's take a look.

When you normalize a file, you alter its overall volume so that the 
highest-level peak in the file reaches a defined limit. The entire signal 
is adjusted in the same proportion, which does not change the relative 
amplitudes of the frequencies within the signal. If the highest peak is at 
the selected limit, the rest of the signal will also be at its highest 
possible level without clipping (distortion) and without affecting the 
overall sound quality.

Compression, in contrast, is used to fit a large signal into a small 
dynamic space by squashing the signal's dynamic range so that the peaks 
are not excessive. But this does not affect the whole signal in a uniform 
way, as with normalization, so the sound is altered. In radio, where the 
dynamic range of the audio signal is usually larger than the receiving 
equipment can handle, compression can effectively fit the audio neatly 
within the limits of the equipment's capabilities. (For more on 
compressors, see "Square One: Dynamic Duos, Part 1" in the December 1994 
issue of EM.)"

Source: http://emusician.com/ar/emusic_youre_air/

Another way to put it, I think, is that normalization is a special case of 
compression- a "uniform upper limit" compression.

I remember seeing compression pedals and controls on guitar and 
mixing gear for years in grade school/high school.  Learning what it 
actually *meant* by playing around with the controls on cooledit was a 
real epiphany for me, and in fact was the beginning of my serious 
interest in computers.  It was my frustration with 
impossible-or-expensive-to-extend proprietary software that led me to go 
to school for it and ultimately to linux and free software.

Bryon




On Thu, 12 Jun 2003, Robert E. Coutch wrote:

> Are you sure you want compression?
> 
> Your original message stated you wanted to remove spikes, etc.
> Normalization does this by bringing the levels to a common amount 
> depending on the sources.  If you have a bunch of .wav's with good 
> levels and one with some spikes, normalizing them will bring levels down 
> in the spiked file.
> 
> If you compress the .wav, all levels will be forced to a common level.
> This will sound like crap unless you decompress later.
> 
> Compression is good for Ham Radio and guitars but not for an MP3 encoded 
> song.
> 
> IMHO
> 
> -Bob
> 
> 
> Russ Schneider wrote:
> 
> >
> >
> > Robert E. Coutch wrote:
> >
> >> I use a program actually named normalize.
> >
> >
> > I read the README/Faq and see nothing on compression, only on volume 
> > adjustment across an entire track.  It sounds like a good normalizer, 
> > and I may grab it, but not a compressor.
> >
> >
> 
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