I Have A 23-year-old Son, Has Always Been Extremely Shy,

I have a 23-year-old son, has always been extremely shy, went off to college each year his voice has become weaker and speaks but a whisper. He has had had a psychiatrist and psychologist. The Psychologist gave him CBT and diagnosed him with extreme anxiety however the psychiatrist has put him on anti-anxiety pill which helps his stress a little bit but the voice still but a whisper. Family members and friends think he may be high functioning autism. I'm looking for a program in New York City during his school break to help him with group social skills; something he is never had. He also had a speech therapist last summer in New York City in which she gave him vocal exercises that seemed to help him when he does practice but nothing really seems to be enough.