Not exactly sure how you created your circle, so I built one in a precomp, a shape with a radial gradient(TRANSPARENT CIRCLE). Duplicated that layer and set the lower one to luma matte to create the transparency(LUMA MATTE). Duplicated again, and turned off the fill and added a 30px stroke(GLOW LAYER). Duplicated the radial gradient layer, placed it above the shape layer and changed the transfer mode to Silhouette Alpha, so that the stroke layer would only glow outwards(Glow Silhouette). Did all this just to isolate the glow layer.
Added audio, selected it, and used Animation > Keyframe Assistant > Convert Audio to Keyframes.
To the stroke layer, I added a layer style glow. And then adjusted the scale of the Glow Layer & Silhouette layer, and glow size to determine my max glow size. Then on the glow layer style layar I added this expression:
The 10 and 30 are the the audio lows and peaks. So when the audio is at 10, my glow is at 10, when the audio reaches 30, my glow goes to 100. You would need to adjust these numbers for you audio. Anyway that's one way you could do something like this. Check out my example file, if anything is unclear. 7301_glowaudiofolder.zip
Johnny Cuevas, Editor
"I have not failed 700 times. I have succeeded in proving that those 700 ways will not work. When I have eliminated the ways that will not work, I will find the way that will work."
---THOMAS EDISON on inventing the light bulb.