Advice on Compressor Effect?

[Justafingerpicker]

Began experimenting with the compressor effect today, with uncertain results. I'm attempting to eliminate the percussive spikes so typical or over-emphasis on drums during a recording. For example...

On a given track, I can tell that the percussion spikes (which really add nothing melodically) are at about 90% normalization. The remainder of the wave file appears to peak closer to 65-70%. If I were to manually compress each individual drum strike at, say, 65% I could get the effect I'm looking for. I'd like to be able to run the compressor to eliminate the spiking, and bring everything down to the same approximate peak level -- WITHOUT having to do every doggone one individually. But I'm getting thrown off by the variables I can specify in Audacity's Compressor effect. Attack time and decay time I think I can figure out -- for percussion, I'm assuming attack time and decay time are both likely to be very small -- but I'm not sure what Threshhold, Noise Floor and Ratio are specifying, so I wind up just playing hit-and-miss until I get a final result I can work with.

Can anybody offer any guidance here, or suggest where I can find it?

[kozikowski]

I think it's possible to force one of the compressors to do this, but this is so perfect for the tool Steve hasn't written yet. Steve wrote the Noise Gate which does things when the sound gets too low. I want him either to rewrite it or fold into the existing tool the ability to do things when the sound gets too hot. The compressors and other tools like them assume you want to gracefully change the volume of the performance as you go louder. That's not at all what's called for.


Try the Hard Limiter. That has few adjustments and I think it's just a whack-off tool (to to speak).

Koz

[kozikowski]

There's also Click Removal, meant to remove cat hairs from your phonograph records.

Koz

[steve]

Try the Hard Limiter.

A "Limiter" is certainly the right effect for the job, though I think that the "Hard Limiter" effect will probably be a bit too aggressive.
There is a more refined Limiter called "Fast Lookahead Limiter" by Steve Harris which I believe is available in the "90 LADSPA Plug-ins" set that you can get from the main Audacity web site: http://audacityteam.org/download/plugins

this is so perfect for the tool Steve hasn't written yet.

Funnily enough I have written something very close to this, but not as a public release plug-in. The version that I currently have is specifically tuned for very aggressive drum compression of Dance music mixes (it deliberately creates "pumping" side effects). I must get round to producing a more general version for public release.

[Justafingerpicker]

A "Limiter" is certainly the right effect for the job, though I think that the "Hard Limiter" effect will probably be a bit too aggressive.
There is a more refined Limiter called "Fast Lookahead Limiter" by Steve Harris which I believe is available in the "90 LADSPA Plug-ins" set that you can get from the main Audacity web site: http://audacityteam.org/download/plugins

I downloaded the 90 LADSPA Plug-ins but when I had a wave file open, I don't see "Fast Lookahead Limiter" as an available effect -- in fact, I don't see any that weren't there before I did the plug-ins download. How do I access them?

[steve]

in fact, I don't see any that weren't there before I did the plug-ins download.

You need to download the file "ladspa-0.4.15.exe" and then run it to install the plug-ins. On Windows you may need to run it as an Administrator. The additional effects should be available when you restart Audacity.

[Justafingerpicker]

After a weekend's worth of experimenting, with inconsistent results, I'm wondering if somebody can help me derive a "common language" between % of normalization and dB numbers.

Referring to my initial post in this chain, suppose I have percussive spikes at about 90% and the bulk of a music file peaking at closer to 65%. I want to get those percussive spikes at no higher than the actual music peak. In my other (much more limited) music editing software program, I can "normalize" those percussive spikes to 65% and achieve the general effect I want.

Can anybody suggest what Threshhold, Floor and Ratio settings might at least get me in that neighborhood?

[Justafingerpicker]

Sort of related follow-up...got the ladspa-0.4.15.exe installed where it belongs, got 'em all. Is there a tutorial for these available anywhere, or any sort of brief description of which one does what?

[kozikowski]

<<<I'm wondering if somebody can help me derive a "common language" between % of normalization and dB numbers.>>>

Everybody likes working in percent, but you run out of range very rapidly because your ear doesn't work in percent. It works in dB.

Maximum volume, 100% or "1" is 0dB.

50% is -6dB.

Half and double are both 6db. 6dB up and 6dB down.

Quiet limit of human hearing is about -60.

Half loudness to your ears is about -20dB.

You can switch the blue waves to dB instead of percent by selecting "Waveform dB" under the black arrow to the left of the show. The bouncing light sound meters always work in dB. You might find it handy to grab the control patch and drag the meters bigger.

http://kozco.com/tech/audacity/Audacity1_playback.jpg

Koz

[steve]

The bouncing light sound meters always work in dB.

The recording/playback meters in Audacity 1.3.x can be switched to a dB (default) or linear scale by right clicking on the meter. The dB scale is generally the more useful option.

I've also just posted a "Quick Calculator" plug-in that can to dB-to-linear and linear-to-dB conversions that you may find useful: http://forum.audacityteam.org/viewtopic ... 46#p100146 If you use it, please let me know how you get on - any sort of feedback would be appreciated.