Humming noise coming from a lamp

Hey there. I recently taped a bar-mitzvah recital in the empty synagogue. There was a lamp fixture situated beside the lecturne, where the boy was reading the Torah. I couldn't notice any interference from the lamp, while I was videoshooting it, but when I came home, captured it, and played it through my amplifier, I could clearly hear a faint humming sound coming from it.
I tried using the 60 hz hum notch filter and kill the 60 hz ground loop filter in Audition with no success.
Is there anyway to kill this background noise?