I've located the two sources of buzzing sounds. The first one is my Coolermaster Hyper 212+ heatsink + fan. The fan's bearing is just noisy but I can live with that. The second source is the hard drive which makes a loud very high pitched whining sound which I can't live with. So I'm going to RMA the drive. The third source of sound which isn't very evident is the power supply which you can hear if your ear is up close to the case.