14.4. Hard Disk Recording with Audacity

With audacity (package audacity), record and edit audio files. This is called hard disk recording. When you start the program for the first time, select a language. At other times, change the language setting under File+Preferences+Interface. The language change is then effective the next time you start the program.

Figure 14.17. Spectral View of the Audio Data

Spectral View of the Audio Data

14.4.1. Recording WAV Files and Importing Files

Click the red recording button to create an empty stereo track and start the recording. To change the standard parameters, make the desired settings under File+Preferences. Audio I/O and Quality are important for the recording. Even if tracks already exist, pressing the recording button creates new tracks. Initially, this may be confusing, because these tracks cannot be seen in the standard-size program window.

To import audio files, select Project+Import Audio. The program supports the WAV format and the compressed Ogg Vorbis format. See Section 14.3.3, “Compressing Audio Data: Ripping” (↑Applications) for more information about this format.

14.4.2. Editing Audio Files

Open the AudioTrack menu to the left of the track. This menu offers various options for different views and basic editing operations. To rename the track, select Name and enter a new name. The different view modes offered by Audacity include Waveform, Waveform (dB), Spectrum, and Pitch. Choose the one suiting your needs. If you want to edit each channel of a stereo track separately, select Split Track. Each channel can then be treated as a separate track. Set Sample Format (in bit) and Sample Rate (in Hz) for each track.

Before you can use most of the tools offered in the Edit menu, first select the channel and the segment of the track to edit. After making your selection, you can apply all kinds of modifications and effects to it.

Depending on the chosen file type, various view formats for segment selections are offered under View+Set Selection Format. With Set Snap-To Mode, the segment boundaries can automatically be adapted to the selected view format. For example, if you select PAL frames as the view format and activate Snap-To, the segment boundaries are always selected in multiples of frames.

All editing tools come with tool tips, so should be easy to use. The Undo History function, accessed with View+History, is a useful feature for viewing recent editing steps and undoing them by clicking in the list. Use Discard with caution, because it deletes editing steps from the list. Once discarded, these steps can no longer be undone.

Figure 14.18. The Spectrum

The Spectrum

The built-in spectrum analyzer assists in quickly tracking down any noises. View the spectrum of the selected segment with View+Plot Spectrum. Select a logarithmic frequency scale in octaves with Log frequency. If you move the mouse pointer within the spectrum, the frequencies of the peaks are automatically displayed together with the respective notes.

Remove unwanted frequencies with Effect+FFT Filter. In connection with the filtering process, it may be necessary to readjust the signal amplitude with Amplify. Additionally, use Amplify to check the amplitude. By default, the New Peak Amplitude is set to 0.0 dB. This value represents the highest possible amplitude in the selected audio format. Amplification shows the value needed to amplify the selected segment to this peak amplitude. A negative value indicates over-amplification.

14.4.3. Saving and Exporting

To save the entire project, select File+Save Project or Save Project As. This generates an XML file with the extension .aup, which describes the project. The actual audio data is saved in a directory named after the project with _data appended.

The entire project or the currently selected segment can also be exported as a stereo WAV file. To export the project in Ogg Vorbis format, refer to the information in Section 14.3.3, “Compressing Audio Data: Ripping” (↑Applications).