Envelopes are OK but if you are editing a vocal track, that can get a bit tedious. And takes too long.
I like to move the track I'm editing to the top so it sets directly under the time line bar. I SELECT THE TRACK.
Now.... I zoom in as far as I need to see the breath sounds and other noise in the wave in the track...
I click and drag on the time line and I see a darker gray section appear in the timeline and also in the track as the "selected" area. Now I go to PROCESS>APPLY EFFECT>GAIN>MUTE
It's quick, easy, and it works well. If you goof up and get too much or not enough.... EDIT>UNDO...and try it again.
I use the mute function all the time and have even used it to remove a click in the middle of a guitar track and it was so fast, you didn't hear the edit to mute and back.....
very useful.