I have a newer HVAC unit that was installed 2 years ago. The outside unit has always made a buzzing sound when kicking on. Lately, however, it seems to have gotten worse. It not only buzzes when kicking on, it also has a periodic, shorter, buzz that occurs while running. It makes a typical humming noise that seems to be pretty loud (although can only be heard while outside), but this buzz is really loud and can be heard inside the house.

The buzz is frequently a high speed, high pressure compressor. Have you had the unit services since installation or has anyone checked your pressure?