Audacity webpage: http://web.audacityteam.org/ "Audacity® is free, open source, cross-platform software for recording and editing sounds."
Example workflow on using Audacity
1. Open a file or record a sound using some kind of microphone. I simply used the microphone of my cheap headset (yes that worked greatly ;-)). You may want to set your recording device to mono in audacity before recording. But you can also record in stereo and then convert the recorded track to mono. Sounds for Urho3D's SoundSource3D are required to be mono, stereo won't work correctly.
2. Remove noise from your recording (may not be needed depending on noise level). (see section below for details).
3. If you want a looping sound: This tutorial http://manual.audacityteam.org/o/man/tutorial_looping.html suggests picking the points where the sound wave is equal or quite close to 0 as the starting and end point. I used this for a steam/thruster sound.
4. Copy your sound to a new track (not really required but makes editing easier).
5. If you want a not looping sound: select a section before your sound and do Effect->"Fade In" to avoid an abruptly starting sound that may cause artifacts in the form of click sounds. Do the same for a section at the end of your sound but this time with Effect->"Fade Out". I used this for two step sounds.
6. Select your whole sound (with fade in and out areas) (if you made an own track for the sound, Audacity has snapping if you grab the starting or end point of the selection for track starts and endings).
7. File->"Export Selection" and save your sound somewhere where Urho can find it (like "Build/bin/Data/Sounds"). I use OGG (.ogg) as the file format (that's like MP3 but patent free and free software and higher quality) and Urho can read it.
Don't forget to save your project if you may need to change things later and re-export. Hint: OGG is compressed with quality loss (like MP3) so you don't want to edit OGG files. FLAC would be an audio format with compression and without quality loss. WAV is an uncompressed audio format (without quality loss, depending on settings).
My project with two step sounds copied to additional tracks. The selected section is where I had clean noise and used the noise removal feature to get clean step sounds without background noise like my PC fans or generic microphone noise or other typical stuff like wind.
A short video showing the steps and the thruster sound effects in-game.
Audacity has a nice feature to reduce noise but made this a bit weird to use so I'm explaining it here in such details.
To remove noise in a recording:
- Select a section of pure noise in your recording (to make this easier: you should record several seconds of "nothing" to have a clean section of only noise).
- Then go to Effect->"Noise Removal" and click on "Get Noise Profile" as seen here:Notice the visible noise in the selected area. The "Noise Removal" window will close.
- Select the area where you want to remove the noise (like the whole recording with Ctrl+A). Go again to Effect->"Noise Removal" and click on Ok (default settings worked fine for me).The noise should be gone now, like you can see here. The noise removal worked great in my cases here. I used that feature several years ago to clean up music tracks with a lot and unsteady and it created distortion artifacts. Maybe they improved that or it really depends on the case and stuff like evenness of the noise.