echo with noisered function

[rust0258]

hi,
I trying suppress background noise in my waves (call record). at
I find Sox very helpful for batch pre-processing.
My issue is with the noisered amount argument, after I generate a noise profile from the original wav (a trim of silence ), the noisered give an output with weird echo and the speech quality change within the output.
is there an specific way for choosing the right amount argument?
can it be generalize for batch pre-processing?

thanks