Boeing 737-800 Airstairs. Ryanair 

It’s of course the sound of the engine’s but a good part of it is from the apu the “extra engine” that gives the plane power on its own fuel

Ryanair is pretty much the only 737 carrier that specs airstairs. Naturally they still need rear airstairs. But that’s also why they do 25 minute turns (40 if there’s a crew change).

Look at the rear door

It's actually about efficiency - less groundcrew needed (↓ wages), no ground equipment needed (↓ fixes assets), quicker turnaround time (more cycles →revenue) = lower prices for the passenger

@@BIZTaxTV - Ryanair really does seek to cit costs where they can. Ironically, they own almost their entire Boeing fleet.