asterisk users - Nov 2014 - detect volume level change on SIP channel

I'm banging my head last few days trying to get volume level on
channel. So far, I tried using sox with no luck.

sox file.wav -r 1 file.dat

gave me volume levels but not before Asterisk finish call recording.

What I really need is to detect volume level change during the call,
say, 30% so I can trigger AMI action.

Any idea?