Looping

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Gale 20Dec13: ToDo-2 Export Selection > Export Selected Audio needed after 2.0.6.
This page provides tips on how to make an audio loop with Audacity.
 
Related article(s):

Contents


Creating an audio loop

To create an audio loop from an audio track, the first step is to find a suitable section. Ideally the sound will be reasonably constant for as long as possible. Looping is much easier with mono tracks, so if you have a stereo recording but a mono track would be sufficient, the track could first be converted to mono using Tracks > Stereo to Mono (see alternative instructions for Audacity 1.2). Loop Selection

The start of the selection should match (look like) the end of the selection as closely as possible.

Gale 26 Mar13: Do we also want the following: "and both selection edges should be positioned so that the blue line of the waveform seems to cross the selection edge at zero amplitude (where the horizontal line appears)."
Audacity 2.0.4 introduces new items in the View menu that allow jumping from one end of the selection to the other while zoomed in:
  • View > Go to Selection Start ( shortcut is CTRL + [  )
  • View > Go to Selection End ( shortcut is CTRL + ]  )
Peter 27Mar13: The exact shortcuts for Go to Selection Start and End are not necessarily decided yet.
  • Peter 23Apr13: we are approaching a potential 2.0.4 release and it doesn't look as though these shortcuts are changing, so I downgraded the P1 to a P2.
  • Peter 3Sep13: The shortcuts did change. I implemented the revised ones and removed the P2.

To look for appropriate loop points, zoom in horizontally on the start of the selection and then on the end of the selection. To zoom, place the mouse pointer at the selection edge and scroll with the wheel or ball. Drag the selection edges leftwards or rightwards as necessary so as to find loop points that have a similar shape, amplitude and slope so that the end of the loop may flow smoothly into the start of the loop. It may also be useful to zoom in on the vertical scale to left of the waveform, as shown in the following images:

Beginning of loop
Beginning of the loop selection.
End of loop
End of the loop selection.

To avoid clicks (glitches) it can often help to use Edit > Find Zero Crossings so as to ensure the start and end of the selection lie accurately on a zero crossing point. In the image below, the sample st the end of the selection (as shown by the dot) is at 0.0 amplitude according to the vertical scale on the left.

Zero crossing point
Zero crossing point.

The loop may be tested using Loop Play (SHIFT + SPACE).

Finding free loops created by others

Try:


Using loops in Audacity

If the loop is to be used in Audacity, the selection may be trimmed: CTRL + T. The loop may be repeated using Copy and Paste, though it is usually more convenient to use the Repeat function: Effect > Repeat.


Exporting Loops

The selection may be exported using File > Export Selection.

The lossless PCM WAV format is the best format for loops. Choose "WAV (Microsoft) signed 16-bit PCM" when exporting. Many lossy, size-compressed formats like MP3, WMA and ADPCM WAV suffer from added silence at the the start or end of the file or other issues that do not respect the exact length.

If a lossy compressed audio format is required then OGG Vorbis may be a better choice as it does not suffer from length issues.

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