Possible to Compress/Limit Input Signal?

Is it possible to use either a compressor or limiter effect in the input signal? When I record a signal (e.g. mic in a large conference room, or a conference phone call) that has a large dynamic range, I’d like to record at a good strong level, yet avoid clipping. I know I can use a compressor or limiter on the already-recorded signal, but is there a way to process it before it’s recorded? I’m running Audacity 2.0.1 on Windows 7 x64 sp1.

You could use a hardware compressor between the microphone pre-amp and the computer audio input.
Audacity does not do real time processing so it is not possible to do that just with Audacity.

Thanks for the speedy reply. Is there any (preferably free) recording program you can recommed that does do real-time input processing, such as compressing or limiting?

Even if there is it would be of limited use.
Any software compressor can only compress the signal after it has been digitised, so in terms of overload protection it offers no advantages over setting the recording level low enough to handle the loudest peaks and then applying a compressor/limiter when the recording is complete. There would however be a downside to real time compressing in that it is not reversible. If you apply too much or too little compression while recording, then you’re stuck with it, whereas if you apply compression after, you can try your settings on a short sample first, and if you don’t like the result you can undo and try again.

Live recording is still one of the holdouts in the automatic audio world. There isn’t one setting that will record everything, although there are laboratory amplifiers and digitizers that will do that, they don’t produce an entertainment quality music file.

What happens when you set your recording for good headroom and just apply the compressors later? The limit in most performances is not high dynamic range, is the competing sounds like room noise, traffic noise, etc. Chris’s Compressor does a very credible job of evening out loudness variations in a show.


Turns out podcasts don’t go through a radio broadcast compressor and they’re almost impossible to listen to in the field/jogging/walking, without constant juggling of the volume control on your iPod. A trip through Chris before you push the show to your iPod solves this.


a large conference room

We can’t take out echoes and reverb. That’s one of the ways to kill a show (#1). You are also flirting with #2.

– The Four Horsemen of Audio Recording (time tested ways to kill your show)
– 1. Echoes and room reverberation (Don’t shoot the show in your mom’s kitchen.)
– 2. Overload and Clipping (Any sound that’s too loud is permanently trashed.)
– 3. Compression Damage (Never do production in MP3.)
– 4. Background Sound (Don’t leave the TV on in the background.)