Investor/RT can handle a variety of sound file types including .wav, .mp3, and .m4a. To review and preview the current sounds available, visit File > Preferences > Sounds. These sounds may be used in a variety of contexts within Investor/RT including Alarms, Signal Actions within indicators (Reference Lines, Signal Markers, TimeAndSales, etc) and even custom quotepage column rules.
To import external sound files into Investor/RT, simply place those sounds into the folder C:\Users\xxxxx\InvestorRT\sounds (replacing xxxxx with your Windows username). After doing so, reopen the Sound Preferences window and those sounds should now be available. If you would then like to automatically create Signal Actions out of those sounds (recommended) simply check the "Create Signal Action for Each Sound Upon Apply" and Apply. At that point, Actions will be created that share the same name as the sound with the word Play in front. For instance, the sound DingDing.wav will have an Action "Play DingDing".