http://www.tftcentral.co.uk/reviews/dell_u2713hm.htm

Update 7/11/12 - We have received a few user reports that the U2713HM exhibits a noticeable buzzing noise when viewing certain content. We have been able to re-create the issue on our sample as well, and it seems to be introduced when viewing full screen content with a lot of text. We've heard the buzz when viewing some spreadsheets full screen, but only when there is a lot of text within those sheets. It's hard to identify the exact cause, but is very rare to experience in practice. Indeed we have used the screen for many hours without problem, but occasionally the buzzing noise manifests itself if the conditions are right. Monitor OSD settings do not make any difference and it doesn't seem to be related to interface connection or anything like that. Not a major issue at all, but worth mentioning for completeness.