I've got the tl350 as well. Some general background noise while recording video, but it isn't really terrible except when zooming in or out. There is a menu option that will cause the microphones to cut out when zooming, that might help. If it is a general background hum, it might be the shake reduction mechanism. I did a short test with and without shake reduction - the video quality was MUCH better WITH SR, and I really couldn't detect much of a noise difference, so I'll be leaving that on.