So if I understand this right, according to Bill, the "mute audio output" that shows "Mute" in yellow across the master output volume, is not working right now but should (when working) silence any sound output from BVC. You talk about .wav files now being played through an instance of Windows Media Player. Does that include sound from the SAPI 5 voice? As of now I do not have any .wav files playing through the system. I am only using the SAPI 5 voice.
Dave, I do have a clear understanding of how the controls work for the windows volume control. The mute button in the playback properties simply mutes the particular input from being directly fed to the output. If that mute box is not checked, the entire room will feed back almost instantly. With that box checked though, it means that from the windows side of things, the microphone will not pick up any sound DIRECTLY from the speaker. On the BVC side of things, even if the microphone is muted under the playback controls in the volume control settings, BVC will still hear what is said.
These are both different than the "Stop listening" command, which from what Dave is saying stops any sound from being heard by the microphone, but only in BVC. If this is correct, then it sounds like BVC needs to be programmed to "Stop Listening" whenever audio is being played.