How to Increase Dynamic Range

I am a new Audacity user. I do not like the fact that most popular CD’s have been compressed for radio play. I see that there is an “effect” for compression, but I don’t see one for expansion, or increasing dynamic range. Seems like there would be one. Can anyone help?

Steve Harris’ SE4 effect is supposed to do this, but I have no experience using it:

All of the plugins I’ve used by Steve have been of high quality, so I’d expect nothing less from this particular one.

If you don’t already have this effect, it’s a part of the LADSPA plugins pack available here, the installation is Operating System specific, so pay attention to that:

You may find that increasing the dynamic range of a show to be a mixed blessing. There are actual complaints on the video forums about having the sound track too good. If you listen to dialog at a comfortable level and somebody fires a gun–or in the case of CSI-Miami, blows up a boat in Biscayne Harbor, my sound system will punch over the oatmeal bowl and scare cats across the street. Now let’s say I lived in an apartment. That’s less good. Now let’s say my SO is trying to sleep in the next room.

Yes, I understand that playing the 1812 that was recorded on Washington Mall with the canons across the river in Fort Meyer may be a problem on a conventional recording, but don’t fall in love with the effect. If for no other reason, these tools tend to have exactly the same problems as compressors–at least four different adjustments, sometimes more–and can create much more damage than is worth the effort.


You are best to seek out “good” recordings. For Classical music, there are magazines such as “Gramophone” that will review the virtues of particular recordings compared to others. The “budget” line of CD’s are rarely top quality.

When a CD is “mastered”, the sound engineer will often use a multi-band compressor to try and create a recording that offers the best listening pleasure for the target audience. With dance music, this is typically to compress it severely to make it as loud as possible. A good orchestral / classic rock / folk / jazz recording will typically offer a greater dynamic range, but they still have to fit the full range of dynamics into less than 16 bit.

The problem with trying to “uncompress” the sound, is that not only do you have to guess how much compression they have used, and at what threshold it was applied, and how hard or soft the “knee” they used, but multi-band compressors apply different compressions to different frequency bands and you don’t know what bands were used. Finally, even if you do know (or guess correctly) these settings, compressors have “attack” and “decay” settings that govern the speed at which the compression is applied. If for example the compressor uses a 10 ms attack and a 200 ms release, then it will take 10 ms of a loud signal before the compressor “kicks in”, and when the sound drops below the threshold, it will take 200 ms before the compressor allows the sound to return to its correct (uncompressed) level. To uncompress this correctly, the expander would need to know if a particular series of samples were compressed because the original level was above the threshold, or because it was within the release phase of the compressor, and there is no way of knowing this.

There are “noise reduction” systems such as “Dolby C”, “Dolby S” and “DBX” that use compression/decompression to increase the dynamic range of audio tape, but even though these use “standard” settings that aim to be reversible, there is still noticeable “mis-tracking” between the compression and expansion.