Install a virtual audio cable app such as VB-Audio Cable, Voicemeeter, or similar
Set Stream Deck soundboard output to the virtual audio cable device
Set the virtual audio cable as the input device in your streaming app or voice chat app
If needed, route the virtual audio cable into your microphone input using Voicemeeter or an audio mixer app
In Windows Sound settings, set the virtual cable as the default playback device only if you want all audio to route through it
In Stream Deck, configure the sound action to use the virtual audio device instead of speakers
In Discord, OBS, Zoom, or similar apps, select the virtual cable or mixed output as the microphone source
Enable monitoring or loopback in your audio routing app if you need to hear the soundboard locally
Adjust volume levels on the virtual cable, soundboard, and mic mix to avoid clipping
Test with a voice recording or test call before using it live