Video Copilot posted a demo, project, and background on Audio Waveforms in AE.
There's more on the Audio Waveform and Audio Spectrum filters in Motionworks video quicktips by Maltaannon Effects A-Z: Audio Spectrum with Maltaannon and Effects A-Z: Audio Waveform, in a 2-part video tutorial by Aharon Rabinowitz, and by Chad Perkins on Lynda.com.
To extend the idea, see Sound Reacting 3D Waveform without 3rd Party Plugins and The Best Sound You’ll Ever See! by Satya Meka from AEtuts. Satya doesn't use a 3rd party filter (i.e., Trapcode Sound Keys), and his techniques present many options. Also, Sam Hampton-Smith wrote up his technique using the Wave World effect and the the CC Ball Action Twist Property in AFTER EFFECTS TUTORIAL: ANIMATE 3D WAVEFORMS USING AFTER EFFECTS.