Weird, weird question- will this support custom noises in the future?
You can actually add sound files yourself and add them to the configuration if you know or learn the simple JSON (Javascript object notation) format.
1. The sound configurations are stored in a text file called "AudioSets.json". I don't know where exactly windows will install Sound Typist on everyone's machine - you'll have to do a search for it. For me, the file is in this folder: C:\Users\andyman\AppData\Local\Apps\2.0\6QE5LO12.B0J\008MWQOZ.NEW\soun..tion_c6713391293800bd_0001.0000_8fb2cfcc9f0f3a91\Resources
For the portable version, it is the Resources folder.
2. Copy your audio files (.wav format) to the Sounds/Misc subfolder under the Resources folder. Make sure they're named very simply and have no spaces for funky punctuation in them. You can get lots of sounds at freesound.org. If you can edit audio files (i.e. using Audacity), make sure you remove any silence in the beginning of the audio file first to increase responsiveness.
3. Edit AudioSets.json in a text/code editor. You can copy one of the blocks of text in there for the existing sounds, and customize it with the filenames of your own sounds, and the name & title. You can also adjust the min/max volume and pitch for some random variation.
4. Quit and restart Sound Typist, and your sounds should show up in the choices. Alternatively, if you don't want to edit the AudioSets.json, you can simply replace any of the existing .wav files with your own .wav files.