Looping a Sound
A looped sound will repeat endlessly without any gap between its end and start. It is up to the sound artist to ensure that the end and start of the file match up however, or there will be a "pop" as the waveform jumps from one shape to another.
Source detects looped sounds ONLY through cue points embedded in the file. This is a WAV-only feature, so MP3s cannot be looped. MS-ADPCM compressed WAVs can be looped, but due to the compression there will be a pop when the sound restarts. (But that can theoretically be avoided for any compressed format, including MP3.)
These free programs can add cue points to a WAV:
Open Goldwave and open the sound you want to loop. Click the cues icon. () Then in the new window click on the New button and add a cue point At Start. Then click New for another cue point and add a point At End. So it looks similar to this:
Your cues do not have to be at the start and end of the file. If you place them in the middle Source will start playing the sound normally, then when it reaches the end cue will loop back to the start cue. From then on only what's between the cues will play.
This can be used to give a sound a "winding up" effect that only plays once (e.g. a motor starting).
Looping an MP3
MP3 files can't be looped with start/end queues like a WAV. A
logic_timer can be a good workaround; have it start playing the sound again after it has fully played (or has played to the point desired).
This could also be done using User I/O from the
ambient_generic to itself, and an input delay.