When using command line parameters to change the listening state, the following occurs:
-listeningoff disables listening; The only indication this occurs is the headset icon on the main window changing.
-listeningon always plays the "Feature On Sound", and enables listening if it's disabled; The headset icon changes when appropriate.
Neither display this change in the log, even though hotkeys and actions do trigger a log entry when changing listening states.
When using the "Make VoiceAttack Start Listening" or "Make VoiceAttack Stop Listening" actions, a log entry and "Feature On Sound" or "Feature Off Sound" are always produced even when the state is not actually changing.
E.G. if the listening state is "Listening", the "Make VoiceAttack Start Listening" action still produces a "Listening Resumed" entry in the log, and the "Feature On Sound".
Some of this may be by design, just making sure.
EDIT: Behavior changed in v1.8.3.22; Command line parameters now produce no sounds or log messages