For anxious flyers, “unusual” noises can get your pulse racing and trigger the imagination (usually for the worse!).

Many such noises are regular occurrences on every flight (such as machinery noises and a thump when the wheels are retracted after takeoff) or occasional but normal sounds (such as a bump when the aircraft is taxiing as it rolls over a taxiway centreline light, or a whirring sound as the cargo doors are closed prior to pushback).  We talk about many of the sounds of flight in our Dragons of Thin Air book. You can also find information and samples of some inflight sounds on the internet, such as the Smithsonian article about aircraft noises. There is no reason for these regular sounds to disturb you, particularly if you already know what to expect.

Sometimes you might hear a more unusual sound, something you have not heard on previous flights. Keep your imagination in check… just because it is unusual to you does not automatically mean there is a problem!

The simple answer to your concern is to ask a crew member about an unusual sound. Of course, a crew member is not always immediately available (they may be seated with their seatbelt fastened; they maybe busy dealing with in-depth discussions about beef vs. chicken with other passengers). When the opportunity presents itself and if you are concerned… ask the question!

However, we can talk about one of those occasional (but perfectly safe) sounds that you might hear on an airliner… the squealing door. Here’s a post I made recently on another forum about such noises:

With regard to the whistling air noise around the door… not all that uncommon. It is simply a seal that perhaps needs replacing… annoying in the noise sense, but not at all a safety risk. The pressurisation system copes no problem maintaining the cabin air pressure despite the extra little bit of outflow. The door itself is a “plug” type door that physically CANNOT open inflight when the aircraft is pressurised (the higher air pressure inside the aircraft over the area of the door pushes against the door, and the leakage of a little air doesn’t change that.  The door itself is “bigger than the door hole” in the same way that a sink plug is “bigger than the sink hole” so this air pressure push against the door secures it and it cannot be opened (in-flight). Quite a clever design, really, as the door mechanism DOES allow it to open outwards on the ground. Some very smart engineers in the world!

While the door seal may have had an air leak (causing the “squealing” noise) that would be permissible (depending on the extent of the noise), and will be inspected by engineers regularly until replaced. Not a safety concern, and if the crew didn’t mention it that is probably because it is not all that rare an occurrence and they would know this. Of course, unknown sounds CAN be disturbing to anxious flyers… you can always ask a crew member about any odd sound that may be concerning you.

In that post I mentioned the “plug” type doors used on airliners. The question is, how can a door that is too big to fit out the door hole (thereby making a very safe door that cannot open in flight) possibly open outwards on the ground?  This video of the ground operation of an airliner door on the ground shows this clever trick in operation…