There is no hum in the audio, but there is hiss. Hiss like that can be caused by any of the following:
a) A mic with high “self Noise”
b) A preamp with high “self noise”
c) A mic witha low output coupled with a poor quality preamp with high self noise
d) Recording at too low a level meaning you need to boost the volume later making the hiss show up louder.
So firstly, if you usea good mic into a good preamp and interface you will not get this problem to start with.
Failing that, as the above poster suggested, invest in Sound Forge. It’s a great program. Use of the Sony noise reduction plugins, Waves X-noise or Izotope RX plugins and any of them will nail that hiss totally if done right.
