Hi Wizboy,
A compressor's function is to reduce the 'dynamics' (differences between loud- and soft phrases)...in music.
In fact, using one will gain-up the noise.

Two ways can reduce noise :
1. The use of a NOISE-GATE will block very low levels. (The 'gate' has an adjustable level)

2. The use of programs on computers that are able to eliminate unwanted signals. These can be : clicks, noise, plosives, hum or even airco-noises ..... just name it !
The only thing you have to do, is 'tell' the computer WHAT to eliminate = get fingerprint.
Activate the 'noise reducer' and after a few seconds your music is as clean as it can be !
Soundforge, Wavelab or Cooledit work excellent.
I always use Soundforge and created copies are better than the originals.

Roel