You can’t adjust the sensitivity of the voice activity detection, sorry. It sounds like it is too sensitive, is that correct? If the issue is that the users are speaking too quietly or from too far away for recognition to be accurate when it is triggered, this is generally something that is best addressed with user education: “MyApp works best if you speak clearly from no more than $DISTANCE away”. If the issue is that utterances are triggering recognition that are not user speech that relates to the app, Rejecto was designed to give a null result under that circumstance rather than a wrong hypothesis. If I have it backward and the issue is insufficient mic sensitivity, you could experiment with the suggestions in this thread:
https://www.politepix.com/forums/topic/add-mode-options-next-version/