Bad Cooked Envelope Data?

Hello, I’m trying to use the “Get Cooked Envelope Data” node to drive the amount my characters jaw is open. I’m building a rudimentary lip sync. However, the values that it returns (used in conjunction with On Audio Playback Percent) is “0.0”. Only after the sound has stopped does it return non-zero values. Almost as if it is inverted. Is there a setting I am missing. Your help would be much appreciated.