i have autism and for me they have always use there hand and lowered it for the first few times they told me what it met then i cought on and now everyone has to do it try that but let his teacher know so she can do it when he is loud to cause i am the very same way and i talk real loud all the time

We did a program with my son where we taught him about using a Number 1 voice (whisper), Number 2 voice (normal speaking voulme), or Number 3 Voice (loud). We modeled those voices for him and had him practice them and had a story about different situations where you would use the different voices. You can get creative and make it personal for his life and even make it a fun matching game to play while he learns. Now when we are somewhere and he is talking too loud i just say, "Pleas use your Number 2 (or whisper !number 1) voice." Hope this helps!

ABA is a good place to start, especially at that age. Loudness can be a way to get attention - positive or negative. A power play. Everyone stops and looks and it can funny to exert that kind of power over and over again. ABA

with my 8 yr old son I've used a 5-pt scale with 5 being danger/emergency down to 1 being no voice at all; 3= normal talking voice, so usually all it takes is a gentle "level 3,please, and he can bring his voice back down. I showed him the chart and reviewed it with him at a neutral time (not when I had just spoken to him about yelling); I shared it with his teachers, too.

My boys are 19 & 20, here is what I have come to find - people with autism don't have sound filters like the rest of us - they aren't loud for attention (though at times - it could be as we all do sometimes!) - they are loud because they are talking over the noise that they are hearing - the lights, the ac, the computer, etc. Take a moment and just be quiet and see how many sounds you can hear - you probably weren't aware of them before - you were filtering the sounds out and focusing on what you wanted to hear. With autism, you don't have this ability to filter out the sounds. I find that when they speak loud, all I have to do is in a voice I want them to speak in, say I can hear you - you are really loud right now, can you talk in this tone please! It's magic and when you have a calm (this is learned - they taught me patience - a miracle!) easy demeanor - it usually calms them down as well! They mirror us! Teach this technique to his teachers as well so there is consistency! Gestures up and down with the tone can help. Hope this helps! :D