From the discussions I have read among the polygraphists who are members of the Association for the Treatment of Sexual Abusers (the largest and most respected group of professionals working with sexual abusers) is that the VSA (voice stress analyzer) has been to be inconsistent and less reliable than polygraph.

I can post your question to some of the polygraphers on the listserve to see if they will respond more accurately to your concerns, if you'd like.
Blissfully retired after 35 years treating sexual abuse