thanks for your reply. it started humming earlier in the week after i bumped the fixture very lightly. it hummed the rest of the day and then went off with the timer at 9 pm. it came back on with the timer at 8 am the next morning and hasn't made a sound since. i think i'll just keep a close eye/ear on it and see if it happens again. every time i have to send one back under warranty, it costs me $14 in UPS charges. (but if it starts humming again, i will surely replace it. not risking hurting Syd) Diane