I live a few miles from a major airport (BOS), under the path that a lot of airplanes use to depart. The planes are somewhat low over my house -- high enough that it's not deafening, but low enough that I can make out the livery. Judging from a couple planes I just looked at on flightaware.com, I'd guess somewhere in the 5,000 - 8,000 foot range.

I can often make out three fairly distinct sounds from the planes:

• a mid-range roar, the sort that one would typically associate with a jet flying overhead
• a sort of whistling
• sometimes a buzz

The buzz isn't always there, but when it is, it's quite loud; significantly more noticeable than the other two.

What causes each of these sounds? I know there are different components of an engine (I'm guessing the main ones for this question would be the fan, compressors, combustion chamber, and turbines, and possibly the nozzle). I'm guessing each contributes to some, but not all, of the sounds.

If it matters, my house is around where the planes turn (they often take off heading more or less NW, and then turn west or SW where I can see them). I think the buzzing (when I can hear it) is loudest when the plane is at about a 45 degree angle to me (so I'm seeing its front-left as it's climbing), but I wouldn't swear to it.