PC World Business

In our previous column we took a look at Audacity (http://audacity.sourceforge.net), a free, full-version audio editing and multi-track application. This time we’ll go through some common yet potentially tricky tasks using Audacity 1.2.0-pre2 (the latest beta version at the time of writing). There’s a copy of both point releases on the PC World December 2003 cover CD.

Audacity 1.2.0-pre2

What you first notice when you start this latest beta are the new inter­face icons and menu options such as Generate and Analyze. The Generate menu includes tools to insert generated noise or silence, and the Analyze menu has two pre-installed analysis tools, including a Beat Finder that has quite a bit of potential.

The toolbox at the top left of the program has been improved (with tools such as envelope) and expanded. The asterisk icon lets you enter a multi-tool mode and the Draw (pencil icon) tool allows you to modify the waveform at the zoomed-in individual sample level.

New playback controls include jump to start, end and pause, and immediately to the right of these is an improved volume mixer. Underneath these are several smaller icons (the edit tool bar) that, from left to right, include cut, copy, paste, trim outside selection, silence selection, undo, redo, zoom in, zoom out, fit selection to window and fit project to window. Clearly, Audacity is becoming more powerful with tools to make editing even easier.

Other new features in the latest beta include the ability to use tracks with different sample rates (quality) within the same project, and some cool time-stretching features.

Time-stretching and pitch-shifting

Traditionally, audio enthusiasts have been forced to use programs such as Sonic Foundry’s ACID (www.sonicfoundry.com) to affect the speed of a sample or sound without altering the pitch, but this can now be done free with Audacity.

Select the portion you wish to affect using the selection tool then simply open the Effect menu and click Change Tempo. You can choose to adjust the tempo using a percentage bar (positive makes it faster, and negative makes it slower) or to adjust the tempo specifically, using beats per minute or length (time) values. The Preview button allows you to test your changes.

You can also change the pitch of a selected track or portion thereof from the Effect-Change Pitch option. Again, you can use the percentage bar to make changes or you can precisely change actual pitch, semi-tone or frequency values.

TIP: If you’re making changes to a selected individual loop within a track, zooming in and pressing the key will help you to get smoother cuts and loops by finding what is known as zero crossing. Also, if you press when a section is selected, that section will play and loop until you press or click the Stop control to end playback.

Reducing noise

We’ve covered how easy it is to record into Audacity. A common use for recording is copying vinyl records. An often-heard gripe when doing this is that the hiss, pops, clicks and static are also captured, sometimes drowning out favourite songs. This column has previously looked at reducing background noise in recordings in Cool Edit 2000 (now discontinued); here’s how to do it in Audacity.

Press -I to import the audio file of your recording, if you haven’t already just recorded it into Audacity. Next, use the selection tool to highlight a part of the recording that has no musical information — just the noise that you wish to remove (try the first few seconds of lead in). You may need to zoom in a bit, as it’s worth being as accurate as you can. With this selected, go to Effect-Noise Removal and click the Get Noise Profile button. Next, press -A to select the entire recording. Go back to Effect-Noise Removal. Clicking Preview will allow you to preview the changes with current settings, or you can use the less or more slider to experiment. Clicking Remove Noise will apply the changes.

With a bit of experimentation, this method can also work for removing vocals and, to a degree, removing the music behind vocals.

Editing MP3 tags

Audacity can open MP3 files straight after installation, but for MP3 export support you’ll need to download a separate MP3 encoder from the Windows download section of the Audacity site.

With this done, when you open an MP3 file, you can easily edit its ID3 tag information — the details that are displayed in many software and hardware personal MP3 players. This is really useful if you’re saving a recording you’ve made to MP3. To edit ID3 tag information, simply to go Project-Edit ID3 Tags.