Both RAM previews and audio previews will honor the "from current time" option in the playback palette or use the work area duration when set. Really basic stuff. You need to read the help...
..;..and in the Previewing section of AE Help, look for the bit on scrubbing audio. Hitting the decimal point key on the numeric keypad is handy as well, because it plays audio from the point of the timeline cursor forward. You can set how long it plays forward in AE Preferences.
Dave LaRonde wrote:
..;..and in the Previewing section of AE Help, look for the bit on scrubbing audio.
However, if you're using version 13 of AE, you might want to hold off on the scrubbing audio part due to a bug. The fix should come out in the next update which is hoped to arrive in 1-2 months.