Well, maybe I'm picky, but on the class C airfeeds,
all these have hum to some extent:
PANC, KBTV, KLFT, KMKE, KLEX, KMHT
Thats 6 out of 8 (working) feeds!
So on the feeder site, how do you read the audio device ?
When you encode to mp3, do you take directly from the device ? If so then you could simply run sox in between and have lame (or whatever libshout uses to encode) encode the filtered output ?
I'm willing to try try setting up a test feeder site (with hum removal) to try it out if you don't have time for it.
We use a variety of UNIX and Linux servers and Icecast for streaming. I don't see any easy way of integrating this into Icecast, at first glance. Sox works great, but the problem has always been finding a place to plug it in.
This happens on so few streams that it would be hard to justify the work required to do this.