Can an experienced airplane spotter identify planes only by sound?

Question

I come from a background in railroad watching, and often times one can identify the maker of a railroad locomotive purely by sound. Maybe not the exact model of locomotive, but at least what type of diesel engine is in the locomotive.

Although there is a similar question here: What could cause GE and Rolls-Royce turbofan engines to sound different?, my question is whether an experienced airplane spotter could be near the end of a runway at a busy commercial airport and be successful in identifying the model of commercial jet aircraft landing and taking off only by the sound the spotter is hearing from the aircraft as it flies overhead?

To me as an inexperienced airplane spotter, they all sound similar. But to airplane spotters, all railroad locomotives may sound the same too. :-)

Answer 1

Yes it is possible, although it is kind of hard to prove it over the internet.¹

When a teenager I lived under the approach path of Westover AFB. My friends and I had no difficulty at all distinguishing among these types by sound alone:

• Douglas DC-3
• Douglas DC-7
• Boeing 707
• Douglas DC-8
• Lockheed L-188 Electra
• Lockheed L-1049 Super Constellation
• Convair B-36
• Boeing B-47 Stratojet
• Boeing B-52 Stratofortress
• Convair F-102 Delta Dagger (singly or flights of two or four)
• Lockheed F-104 Starfighter (singly or flights of two or four)
• North American F-100 Super Sabre (singly or flights of two or four)

We only looked up when some other type flew over.

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1. This line is an homage to kevin who said it first.

Answer 2

Yes it is possible, although it is kind of hard to prove it over the internet.

Generally the type of engine (propeller / turbo-fan / turbo-prop etc.) is quite easy to distinguish as they make very different sound. I can also tell a Rolls Royce engine from others because Rolls Royce engines make a quite "harmonic" and "warm" sound as it powers up.

Now here is the fun part: I correlate the sound with the type of the plane by comparing the Doppler effect as the plane passes by. It tells you how fast the angular velocity is in relation between you and the plane. The variation in loudness gives you the approximate distance to the plane - if the plane is far away, its loudness would change slowly. Combine that with the geographic location of yourself and the flight paths of planes, it gives you the speed of the plane.

The speed of the plane is important because it tells you the size of the plane. If I hear a loud multi-prop engine moving slowly, I'd bet a transport plane, something like a C130. If it is moving quickly, I'd bet an aerobatic aircraft.

The location where I live is directly under one of the SIDs of a major airport. Planes are usually ~3,000 feet when they pass above me. One thing I notice is that long route planes like Boeing 777 or Airbus A340 makes a noticeably louder noise. This is because these planes carry a lot of fuel on takeoff, and their climb performance is restrained compared to short haul airplanes, meaning they pass above me at a lower altitude, hence the louder noise. I cannot distinguish from sound if it is a B777, B747, A330 or A340, but I know it is not a B737 or A320 unless the pilots fly slow and low.

_{I confess I have an unusually good hearing ability. I often hear faint sound or noises which others cannot notice. I am also a musician.}

Answer 3

A few years ago I was camping at Download Festival with a friend who is a 747 pilot. When we weren't watching bands we spent a fair bit of time in our tent playing the "identify the engine" game as aircraft took off from East Midlands airport right over our campsite. She was pretty successful, pointing out the differences between jet engines, discussing the difference between a Graunch and a Whine, such that I can now easily distinguish between a Rolls Royce and a GE engine, between 2 and 4 engines, likely airframe (based on launch noise and volume) etc. So generally, yes, you can distinguish between many types of aircraft by noise profile.

One stumped her, though - and I identified it as a C-130 (from my years in the Falklands this was a familiar sound) so we watched it go by and then got back in the tent.

The next noise we heard was something neither of us could identify. So we climbed out of the tent - as did everyone else around us. The loud, earth-shattering roar that increased in volume was the Antonov AN-225 Mriya taking off almost directly overhead. Never going to forget that one.

Answer 4

Yes and no. The heard sound depends on aircraft's speed, altitude, surface positions (flaps, AoA), gear, weather (especially wind direction), other external noise (e.g. nearby busy roads) and of course engines (big proportion).

So a "resident planespotter" like @kevin can clearly identify aircrafts very well just by sound. At a different airport with different environment conditions (especially different approach procedures), it is much more difficult.

By the way, the aircraft dependent noise (engines, gear, flaps) is studied and optimized during design of an airplane.