Anyone who has stood near an airport fence watching aircraft take off and land will likely have noticed the difference in noise levels between certain types of aircraft. Today’s commercial airliners are significantly quieter than their predecessors, thanks to decades of technological advancements in engine design, aerodynamics, and noise mitigation strategies. But what exactly makes the latest generation of jet aircraft so much quieter? Let’s take a look.
Engine design and the shift to High-Bypass Turbofan engines
One of the biggest reasons for reduced noise in modern jets is the widespread use of high-bypass turbofan engines. Early jet airliners like the Boeing 707 and Douglas DC-8 were powered by low-bypass or pure turbojet engines, which generated significant noise due to their high-velocity exhaust gases.
In contrast, today’s commercial aircraft, such as the Boeing 787 and Airbus A350, use high-bypass turbofan engines like the Rolls-Royce Trent XWB and General Electric GEnx. These engines feature a much larger fan at the front, which pushes a greater volume of air around the engine core rather than through it. This ‘bypass’ airflow reduces the velocity of the exhaust gases, significantly lowering noise levels.
Low bypass engines tend to produce a tearing or cackling sound, which resonates through the air when the engines are at full power. This was especially notable with early jet age aircraft such as the first Boeing 747s, Boeing 707 and Vickers VC10. As noise abatement rules came into effect at many airports, attempts to reduce the noise made by low bypass engines were made, such as ‘Hushkits’. These attempts generally met with limited success.
Whilst the difference is notable between early jets and the latest generation of jetliners, a notable difference can even be heard when observing more modern passenger jets such as the Airbus A330ceo and Boeing 777. For comparison, an Airbus A330-300 built in the early 2000s typically puts out around 107 decibels of noise at takeoff thrust when observed from 600 meters away. The updated Airbus A330neo produces just 90. According to Airbus, the A330neo approximately halves the overall noise footprint area compared to the A330ceo.
Advances in engine materials and noise dampening features
Modern jet engines also incorporate advanced materials and design improvements that contribute to quieter operations. One key innovation is the use of chevrons. These are serrated edges on the trailing edge of the engine nacelles and are seen on aircraft like the Boeing 787 and 737 MAX. These chevrons help mix the high-speed exhaust with the surrounding air more smoothly, reducing the shear noise that occurs when two different airflows interact.
Additionally, improvements in fan blade aerodynamics and composite materials have led to quieter fan operation. Newer engines have fewer, more aerodynamically efficient fan blades that move more air with less turbulence, further cutting noise levels.
Aerodynamic improvements
The overall design of modern aircraft has also played a role in reducing noise. Older aircraft designs often had less efficient aerodynamics, causing more drag and requiring engines to work harder (and louder). Today’s jets feature smoother fuselages, raked wingtips, and quieter flaps and slats to optimize airflow and reduce noise during takeoff and landing.
Landing gear noise, another major contributor to overall aircraft noise, has been addressed with fairings and improved strut designs that minimize the turbulence caused by extended wheels.
Beyond technological improvements, modern aircraft are also quieter because of strict noise regulations. Organizations like the International Civil Aviation Organization (ICAO) and the Federal Aviation Administration (FAA) set stringent noise limits for new aircraft designs. These regulations have pushed manufacturers to develop quieter planes that meet or exceed noise reduction targets.
Other techniques
Noise abatement procedures on takeoff
Airlines also use noise abatement procedures, such as reduced-thrust takeoffs and steeper climb angles, to limit noise impact in communities surrounding airports. These operational changes, combined with quieter aircraft, have helped make air travel significantly less disruptive than it was in the past.
Here’s an example of a noise abatement procedure at London Heathrow Airport (LHR).
Here is that procedure in action as seen on Flightradar24. If you compare with the chart above, you can see the Gulf Air (GF/GFA) aircraft is following the Southeasterly noise abatement procedure for runway 09R, whilst the British Airways (BA/BAW) aircraft is following the Northeasterly procedure.
Noise reduction on approach and landing
Another technique that reduces noise around airports is the Continuous Descent Final Approach, or ‘CDFA’. This involves a steady descent from cruising altitude to the landing airport, as opposed to the more traditional method of a stepped descent, where the aircraft descends and maintains a series of given levels. The CDFA is heavily favored by airlines because it requires minimal changes in engine thrust, saving fuel and, by extension, making less noise.
Do you agree that aircraft are getting quieter? Let us know in the comments.
Cover photo: Owen M, JetPhotos
15 Responses
And current airliners cruise SLOWER than a 727!
Definitely getting quieter. Having recently flown an itinerary that consisted of a B717, a CRJ9, a B772 and an A359, the difference as a passenger is also very clear.
Early jet airliners were powered by turbojet with no bypass which were seriously loud. Even the Trident 3 had low bypass Spey engines with an added turbojet for improved take off performance, deafening
More of a question please. Sometimes newer jet engines seem to make a noise a bit like a low revving motorbike engine. I’ve noticed it esp when climbing. …. ?
Another explanation is that little by little I became deaf.
Yes, esp. larger Airbus aircraft, the A380 upper deck is sublime, even on T/O. I’m not sure some crew appreciate just how much quieter the A350/1000 (Virgin) is compared with A333 and even 787. A recent LAX-LHR night flight wearing N/C headphones, I could hear intricate details discussed in the galley, of their night out in LA, they weren’t be loud but the a/c is so quiet, upfront especially.
Impacted by noise since NPR opened in Brisbane, Australia.
Aircraft technology may have improved, but an A380 40km from runway creates a 95dB SEL cutting through minimal overnight ambient noise. Brisbane Airport Noise Monitor Data.
Airlines do not adhere to ICAO preferred NAPD1, they use NAPD2.
Flight paths design are flat due to layering and concentrating flight paths over the same communities. This includes turbo prop, aged general aviation under jet paths.
Absolute failure for our communities
Still a LOT more the aircraft makers can do. Flying in the A380 is the best experience because it is so quiet. I sometimes don’t even realise it has lifted off the tarmac at takeoff.
Even Boeing’s most modern aircraft are noisy and harsh by comparison. Airbus has obviously spent money on passenger friendly features like sound deadening, and Boeing just dispensed with them to save money.
most aircraft seam to be quieter the main problem is there are more and more every year I live under the approach to Birmingham Airport in the warmer weather I and many other people can not sleep with the windows open due to the noise aircraft approaching from the north they now seam to be coming in 24 hours a day could they make a steeper approach with the power reduced p s I live far enough away not to be affected by departing aircraft
During my childhood in Bombay, I still remember the taking off noise created by the Caravelle was one of the most loudest of them all!
Indeed, Anthony, my sister stopped any conversation when the VARIG Caravelle started over her house, just a mile from the Congonhas Airport’s runway in Sao Paulo / Brazil
Toni
This is my own anecdotal evidence 5 miles from Bournemouth airport but outgoing overflying 737Max aircraft are noticeably quieter than older 737-800 aircraft.
Jet airliners of yesteryear eg B707 and BAC One Eleven (built at Bournemouth) were shockingly loud.
Yes aircraft noise is significantly less in the last few years. I grew up with Tristar court airlines aircraft over home. They were loud. Nothing here is loud as they were lol.
I see a lot more early turning away for from built up areas and wider more considerate routing.
I’m quite impressed with local changes.
One thing which seems to have been abandoned is delayed landing gear. Gear makes a lot of noise but I understand if that’s for safety reasons.
Hello David, yes that’s happened about a decade or two ago; that’s because the ICAO determined that safety of landings is considerably enhanced if an aircraft is stabilised by 1000 feet above ground.
Being stabilised means that the aircraft has to be in the landing configuration (gear lowered, flaps out, thrust above idle…). To get there, we have to start lowering our landing gear and flaps at around 2000 feet such that they are down and locked by 1500 feet and the approach speed reduces to landing speed by 1200, so that the thrust can open from idle and settle down to the approach thrust by 1000 feet to go. All this is probably why you are seeing aircraft with their gear down a lot earlier.
Anybody remember those roaring DC-9s?