Backwards

Description
The Backwards effect reverses the audio of a layer by playing the audio from the last frame to the first frame. The frames remain in their original order in the Timeline panel. Select Swap Channels to swap left and right channels.

Harry Frank and Aharon Rabinowitz provide a video tutorial on the All Bets Are Off website that shows how to use the Backwards effect and the Reverb effect to create a creepy reverse echo result.

Parameters

 * Swap Channels :Swaps audio channels

Reference

 * http://help.adobe.com/en_US/AfterEffects/9.0/WS3878526689cb91655866c1103a9d3c597-7bb9a.html