I took a listen to the webcast signal when I got home. Man, that whine is horrendous. Furthermore, the hum is present when most of the station equipment is powered off, so clearly the source is not in the main studio, but something in the production studio where the webcast encoding computer is located. I sent off an email to the general manager of the station, but I haven't heard back yet. Hopefully we can sort this situation out before next Friday.