What’s That Noise?

Let’s face it – plane journeys are a noisy affair with all the mechanical equipment buzzing and whirring. The noises themselves can add to worry about flying – what was that thump? Was it a bang? Is that meant to happen? Both loud noises and decreases in noise levels can cause anxiety during flights. So let me explain what some of the noises you may hear mean. Remember all planes are different so this is just a general guide.

On the Ground
At the airport when you first take your seats you can expect to hear some banging sounds coming from underneath you and possibly some shaking of the plane. It could be the cargo being loaded onto the plane in the hold below, or the catering supplies arriving in time to be devoured by you on your flight.

The Auxiliary Power Unit (AUP) usually keeps everything running on the plane while the main engines are off and this includes the power source for the air conditioning. It can normally be heard as a high pitch whirring. The power can be transferred to the engines so there can be changes to the intensity of air coming from the air vents during this time.

Whining noises can often be heard as the plane gets ready for take-off. It’s usually because the pilot is extending the flaps on the wings to make the wings much wider than usual. The slats can be extended as well to help provide sufficient lift for take-off.

Take Off
The main noise in this phase is the sound of the engine accelerating to give the plane sufficient speed to lift off the ground and climb into the sky. The sound is created by the high-speed air coming out of the engine hitting stationary air. Once in the air, the landing gear is retracted into the plane. This is hydraulic powered so you may hear a whirring noise sometimes followed by a loud thud. The wings flaps are then retracted and return to their usual position, repeating the same whining noise you heard when they were being extended.

The “Ding Dong” chime that normally occurs before the fasten seatbelts light goes off is to signal to the flight attendants that the aeroplane is above 10,000ft – the minimum altitude where they can begin providing food and drinks to passengers. You‘ll probably notice the flight attendants move out their seats and start going about their flight duties.

Flight
Once at the required altitude the plane will start levelling off to continue at cruising altitude. Just like when you have climbed a hill in a car or on a motorbike, you reduce acceleration and so the sound of the engine noise is reduced. For people who are anxious, sometimes it can seem like the engine has actually stopped, given the huge difference in sound levels. Rest assured, this is usual at this stage. There are not many changes in the noise level during the cruising stage apart from changes in altitude levels to find the smoothest flight path, and most of these changes are unnoticeable. Sometimes the Captain will want you to fasten your seat belt, if you are approaching a bumpy part of the flight. The “Ding Dong” chime will sound, which means you then look up at the overhead panel to see if it is anything to do with you. You may then see that the seat belt light is now on, so back to your seat you go, if you are standing in the aisle going to or from the toilet, and “clunk click” you fasten your seatbelt. Returning to your seat and wearing the seat belt is a safety precaution, to prevent you being bumped around. Do remember that turbulence is a comfort issue, not a safety issue!

Descent
Most the noises heard at this stage are the reverse of the take off. First the engine noise increasingly reduces as the plane decelerates, and you slowly begin your controlled descent. There may be a chime to signal you are now below 10,000ft again. Spoilers may be used to increase drag and slow the plane down further. These are the flaps on top of the wings which can induce an audible rumble and vibration in the cabin when they are raised. The wing flaps and landing gear are extended with the associated whirring and whining.

Landing
Once the wheels have touched down the reverse thrusts are engaged to slow the aircraft down quickly. The engine sounds like it is speeding up and you feel yourself forced forward due to rapid deceleration. Once the plane has slowed to taxiing speed, the APU takes over and you will hear the associated high pitch whirring.

If you have a seat near the wing of a plane it is worth watching how the wings work during take-off and landing. It can be fascinating to see how they move and adjust through the process. You’ll see the wing flex at times, and you can tell yourself this is what it is designed to do. Becoming familiar with the sounds you can expect during a flight can help ease fears about flying but for further help see my courses and self-help treatments.