Have you ever been outside and heard a jet aircraft taking off? Have you ever noticed that — particularly when it’s a larger aircraft — it makes a sound that more closely resembles the buzz of a prop plane than the whoosh of a jet?
I used to be incredibly mystified by this. As an 11-year-old, I got Microsoft Flight Simulator 2002, and went straight to the jets. All of the takeoffs that I ever did — whether it was a 747, 777, or 737 — all featured high-pitch sounding jet engine noises. Furthermore, whenever I flew as a kid, I pretty much always ended up sitting behind the fan of the engine, where takeoff noise sounds much more like an incredibly loud fan. However, after finding myself living under the majority of Runway 33L departures from Logan, I began to hear a lot of jets — particularly those taking off or climbing out — that sounded like they were an engine being revved up so high that it made some sort of a “grinding” noise. I set out to figure out exactly what it was, and I was surprised by what I found.
It turns out that this “grinding” noise actually has a name: the buzzsaw effect. When a plane takes off, it (often) has its thrust levels set at TOGA, which stands for “takeoff/go-around.” When this happens, or indeed when the thrust settings are high in general, the blades in the fan of the jet engine itself are actually moving faster than the speed of sound. As a result, a buzzing noise is generated, and that’s where the buzzsaw noise that you hear comes from. Obviously, I’m providing a very high-level explanation here, but now you have a basic understanding of where this mysterious noise is coming from.
Hearing the Buzzsaw Effect
One caveat to the buzzsaw effect is that one generally has to be situated in front of the engines themselves to hear the noise. This is why, on aircraft with fuselage-mounted engines such as the Boeing 717, most passengers can hear the buzzsaw noise generated. However, on aircraft with wing-mounted engines, this “privilege” is usually reserved for those sitting in front of the wings. Similarly, the buzzsaw can be heard by someone standing on the ground as the plane approaches, but the effect dissipates somewhat after they are left in the plane’s wake, as is demonstrated in the video here.
Which Planes Have a Pronounced Buzzsaw?
It’s been well-established that the British Airways 747-400 is my favorite plane, but its Rolls-Royce RB211-524 engines have one of the most incredible buzzsaw effects in my opinion (the first 1:30 of the linked video is worth a watch). When I started seeing these planes on a regular basis, the first thing that I noticed was that they seemed to possess a unique-sounding engine — sounding “like a grinding noise” as I once described it to my father, or perhaps more accurately a “growl.” Other 747-400s with General Electric and Pratt-Whitney engines have similarly impressive buzzsaw sounds, but I prefer the Rolls-Royce engines. I might be biased.
Also in the four-engine category, the Airbus A340-300 has a similarly impressive buzzsaw sound, even if its CFM56 engines are about half as powerful (34,000 lbs. thrust) as the RB211-524s (60,000 lbs. thrust). Many, myself included, have derided the A340-300 and its CFM56 engines — which, for perspective, also power smaller aircraft such as the Boeing 737 and Airbus A320 — as being like a loud poodle: strong in terms of volume, but not powerful like the Trent 500 engines that power its big brother, the A340-600. Regardless, the A340-300 has a pronounced buzzsaw noise, and that can’t be disputed.
The buzzsaw is not exclusive to those two planes, however. The Boeing 777 and Airbus A330 have buzzsaw effects that can be heard, and even smaller aircraft like the 717, 737, and A320 have noticeable buzzsaw sounds, as does the Boeing 757 shown here. Even newer, quieter aircraft like the Boeing 787 and Airbus A350 and A380 have audible buzzsaw noises on takeoff and climbout.
While the average person might perceive the buzzsaw effect as being obnoxious, I actually find it kind of charming. For me, it illustrates the sheer power that jet engines possess. Think about it: these things can get aircraft that — in the A380’s case — can weigh over a million pounds, and get them to travel thousands of miles at rates approaching the speed of sound. That is pretty incredible.