Ever wondered why your airplane was making that sound? Curious as to what that whirr, rumble or even the noise of a barking dog (no really) from under your seat was? If you tend to worry when you fly, let us put your mind at ease with an explanation of some of the most common noises you’ll hear on a flight.
Bings and bongs from the overhead speakers
Pilots and flight attendants use the bing-bong sounds pretty often to communicate, whether that’s to simply inform each other of something that’s going on – like that takeoff or landing is imminent, or that the plane has reached the altitude where the first drinks round can begin – or to signal that they should pick up the intercom.
Relax: the only thing to worry about is whether you want a gin and tonic or Bloody Mary.
A change in the amount of noise (and wind) coming from the air conditioning system
Systems on airplanes are interlinked, and the amount of air blowing through the vents above your head can vary depending on whether either the power of the aircraft or the air itself is needed for other things.
This might be when pressurising the cabin, since the atmosphere inside is kept at 6000-8000ft even when you’re 40,000ft in the sky, or it could be in preparation for takeoff, or when the plane climbs.
It could also be the result of a change in the source of electrical power the plane is using. On which note…
Read more: Why do we have to raise airplane window blinds before landing?
Flickering lights, and the noise of systems spinning up or down
Don’t be alarmed if the lights flicker, especially on older planes: this is usually the result of changing the source of electrical power the aircraft uses.
That source is usually either power from the engines, power from the auxiliary power unit (the APU, a sort of generator at the back of the plane), or ground power when parked.
You might also hear the sound of fans or other systems spinning up or down: nothing to worry about, this is just the pilots getting the plane ready to go or parking it up.
Rattling from the overhead bins
If you hear the overhead bins shaking about a bit, especially on takeoff and landing or during turbulence, don’t be alarmed: they’re designed to shake around a little bit and they’ll be perfectly fine. Just keep an eye out for falling luggage when you open them.
A whining or roaring noise at the back of the plane
Remember that APU? If you’re seated at the very back of the plane, or boarding from the back via stairs, you may well hear the roar of what is usually a mini-turbine engine that adds extra power to the plane.
It’ll often start up when ground power is disconnected, or if you’re parking at a remote stand without a jetway directly to the terminal.
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Gear shifting sound of engines
It might sound a little bit Formula 1, but engines, especially new engines, can sound as if they’re shifting gears. That’s entirely normal for them as they spin up from a standing start in particular or the pilots apply power to begin takeoff.
A series of bumps on the runway
Don’t worry, this isn’t the plane running over anything it shouldn’t! It’s either the joins between the sections of the runway, which like bridges are designed to expand and contract with heat or cold, or it’s the wheels rolling over the lights on the runway.
Like the cats’ eyes reflectors on a road, these lights are also designed to take the impact of wheels on top of them, although most pilots will try to line the plane up slightly left or right of them to avoid the bumps.
Rumble-thump after takeoff, and a thump-rumble before landing, often with some whooshing
The noise of the landing gear being retracted back into the aircraft by the aircraft’s hydraulic systems can be a bit of a surprise to some passengers, especially anyone seated at the front of the plane or near the wings.
The nose wheel, in particular, can make a bit of a racket as its tyres are braked to a stop and the landing gear’s door flaps close up.
Engine noise diminishing at the top of descent
The pilots of most modern planes will start their landing procedures by throttling back on the engines quite a ways away from the airport, since most planes come in for landing at a three degree angle.
(Frequent travellers will often use this as a handy cue to pop to the lavatory before landing if an announcement hasn’t already been made!).
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Rumbling noise sometime before landing
Since the most efficient wing shape at takeoff and landing is different from that of the cruise phase of flight, planes use extending sections of wing called flaps and slats to change the amount of lift they generate.
These extend during takeoff and landing and are retracted once the plane is at its cruising height.
You might not notice these retracting bit by bit during takeoff, but they’re more noticeable during landing since there’s a bit of a rumble when they extend.
Mechanical and wind noises plus a thump on final approach
The last noise you’ll hear before the double bump of landing is some mechanical sounds, wind noise and a thump as the landing gear doors open, the gear extend and everything locks into place.
That’s your cue to double-check that your bags are well underneath the seat in front of you, that any larger electronics are put away and you’re set for landing.
A dog barking under the plane
Lastly, if you’re on an Airbus plane, don’t be surprised if it sounds like there’s a massive woofing dog underneath the floorboards when the plane is on the ground!
It’s unlikely to be Fido down there in doggy class – rather, it’s a system that adjusts hydraulic pressure when the pilots are using just one engine, like at startup or when taxiing more efficiently.