Identify the hissing track. Hit "Play" and click the "M" icon on the track at the top of the channel strip to mute the track. Work your down the tracks, muting each one separately until the hiss disappears. Once the hiss is gone, you can identify the muted track as the source.
Press the "S" icon on the track to "solo" it; this mutes everything else.
Click "Tools," "Equalizer." This tool lets you boost and cut various frequencies. Hissing sounds have a limited frequency range that is uncommon to other sounds. By cutting the frequency range on which the hiss exists, you mute it without influencing other sounds.
Click "Band." Soundbooth has a preset EQ function that automatically shapes the frequency curve of a sound to predetermined parameters. Bypass this and manually narrow each frequency band until you hear the hiss receding.
Drag the slider dial for the hiss frequency to zero. This cuts the gain of anything in that frequency for the duration of the track, silencing the hiss.
Identify the hiss. Play the track and when you hear the hiss, rewind it. Solo the first track and play back. Repeat this process until you hear the hiss in a soloed track. Intermittent hisses are audible only when there is a gap in the audio track that creates them. For example, a hissing guitar can be heard only when the guitarist stops playing.
Click on the offending track. Select "Zoom" to enlarge the sound wave graphic. Play it back and follow the timer bar to identify the sound wave that corresponds with the hiss.
Highlight all of the audio, up to the point where the hiss appears. Click "Edit," "Crop." This separates the file into two. Click on and delete the sound wave that corresponds to the hiss. Repeat this process for all subsequent hisses.