Calibrating Audacity

[mdlbear]

One thing I forgot to mention from the weekend was the way I calibrated Audacity's latency compensation. The current stable version, 1.2, does a pretty good job of synchronizing newly-recorded tracks with what was playing when you recorded them, but it's not perfect and not adjustable. The new version, 1.3, has adjustable compensation. Unfortunately, what comes out of the box is practically unuseable -- there's a huge lag, and at first I compensated by time-shifting the new track by hand, which is obviously highly error-prone.

So Saturday afternoon, before I did any actual recording, I calibrated it. I recorded a dozen seconds worth of clicks (by tapping my guitar's pick guard with a fingernail, which gives a nice sharp attack), then cranked the volume up and recorded a track with the appropriate earpiece of the headphones held up close to a mic.

I still had to amplify the resulting track by 30dB in order to actually see the resulting waveform -- headphones are meant to operate in a small, closed volume. But it worked. (Note: "amplify" is the first or second on the menu of built-in effects.) (Hint -- vary the click pattern so you can see which direction you have to adjust.)

The way you get the exact timing between clicks is to zoom way in and select the gap. Set the selection display at the bottom of the screen (another new Audacity 1.3 feature) to show the selection length in milliseconds.

After a little trial-and-error, I found that the correct latency compensation for my setup was -140ms. There's also a buffer parameter which defaults to 100ms; I cranked it up to 200. Don't know whether I had to or not, but it seemed like the right thing to do.

Q.E.F.