Audacity on Ubuntu Linux

Features

• Record live audio
• Record computer playback on any Windows Vista or later machine
• Convert tapes and records into digital recordings or CDs
• Edit WAV, AIFF, FLAC, MP2, MP3 or Ogg Vorbis sound files
• AC3, M4A/M4R (AAC), WMA and other formats supported using optional libraries
• Cut, copy, splice or mix sounds together
• Numerous effects including change the speed or pitch of a recording
• And more! See the complete list of features: http://audacity.sourceforge.net/about/features

Howto

Howto Export to Mono

The mp3 options channel mode is misleading. Even though it says "stereo", it will (can) eventually export a mono file. If the "use custom mix" options is turned on in the menu:

File -> Preferences -> Import/export

After the change then you will note an advanced mixing dialog will appear before the file is saved, and you can verify the file will be saved with 1 channel (i.e. mono).

In the next 2.1.3 version of Audacity when released there will be a "Force export to mono" checkbox for when you have a stereo track, but a mono file will still be exported from a mono track even if that checkbox is not enabled.

From the developers: The "joint stereo/ stereo" options refer to the "channel mode" command that Audacity sends to LAME (which encodes the MP3). Lame only uses that command if the audio is being exported with two channels. If Audacity is sending single channel mono for encoding, then LAME ignores the channel mode instruction. The settings in the MP3 options control all subsequent MP3 exports until the user changes the settings. The "channel mode" instruction can't be "greyed out" when exporting a mono track because if the channel mode option is not set then LAME will not know what to do if the next file to be exported is a stereo track. The MP3 options do not only apply to the current exported file, they apply to all exported MP3 files.

Change Sample Rate and Achieve Smaller Export File Size

If you change the project rate (in Project Rate box in the lower left of the main Audacity screen) to a lower rate before exporting, the encoded MP3 will use that sample rate and produce a smaller file.

Reducing the sample rate will also reduce the frequency band limit (the maximum frequency at a given sample rate is always less that half of the sample rate). If you are only interested in the intelligibility of the voices, you can probably go down to around 16kHz sample rate (which will limit the upper frequency response to around 7kHz) and still have acceptable quality.

If you have a track already recorded at a higher sample rate then you can resample it to a lower rate. In the menu choose Tracks -> Resample. After you resample so the resulting track sample rate is much lower, then you can export and get a yet smaller file size.

record onto same track

Hold SHIFT and click Record (or SHIFT + R) to record at the end of the selected tracks(s).

You cannot record over a mistake or over any existing area in the same track (known as "punch-in" recording). You will have to record on a new track underneath to do that, by clicking "Record" or using the "R" shortcut.

You can delete selected tracks with the Tracks > Remove Tracks command, for which you could add a keyboard shortcut by clicking Audacity > Preferences: Keyboard