audio stopped working

The audio for all of the footage in the video I'm editing went haywire. I think it's because I clicked "volume" under "track frame" for a single row/line of audio, and after I figured out how to unclick the "volume," the audio for the entire video stopped playing. I know it's not my speakers or an audio output problem because when I playback the video, the audio level meter has no movement at all. Also, even though the audio is "linked" to it's corresponding footage, now when I edit the footage, nothing happens to the audio and I have to select both the audio and footage in order to edit them together. I'm not sure what happened or if I accidently changed a setting! Help!