asterisk users - Sep 2005 - sox conversion has introduces background hiss for both 8k and 41K recordings to gsm

I took a recording that was in 41k sampled mono wav. Did the sox 
file.wav -r 8000 file.gsm resample ql
took an 8K record in wave did sox file2.wav file2.gsm

Both of them have introduced a hissing noise.
If I play the wave files they sound fine.

How do I remove or reduce the hiss.

Jerry