Question

I opened a song a heard a low hiss. I checked the tracks and some of the tracks were showing low level volume on the VU. See picture. I created new tracks and brought file over to the new track which corrected the problem for a minute and then the hiss came back. Thoughts?

Answer 1

Do you have de mix fx on the master? This van create noise and crosstalk on empty tracks.

Answer 2

Are the inputs on those tracks all set to "None"?  Did you add any plugins to the tracks?

Answer 3

I had the same problem a few hours ago, and I discovered this hiss was triggered by plugins that had an analog option. 

The Waves H Delay plugin has an analog setting, I turned the analog option off, and the hiss was then gone on that track. 

The Waves PuigTec EQ plugin has an 50Hz/60Hz knob. I turned that knob to “off”, hiss gone.

Hope this helps.