Sound in planes

[codash1099]

Regardless of personal airvents or not i like fresh air. And i really notice down the back of some planes the air is really not very good, am i imagining it or is it really like that ?

That's because there's a whole airplane of bums pointed in that direction.

 

[Ritzy]

This is not quite correct. The aircraft is not pressurised to maintain sealevel pressure. At cruise, the pressure inside the cabin of a modern airliners will be the equivalent of between 6,000 feet and 9,000 feet. One of the benefits of the 787 noted by Boeing is the ability to operate with a 6000 foot cabin pressure, however airlines choose to reduce the cabin pressure to closer to the 8000 feet commonly used by most airliners now. Larger changes in cabin pressure pose more stress on the aircraft and require more regular maintenance. The process of pressurising and depressurising the cabin affects the life of the hull.

Not all air the flows into the cabin is fresh air. A proportion of the air that is fed into the cabin is recycled from the existing cabin air. Some fresh air is required to replace that which is exhausted via the pressurisation values. In the past when smoking was permitted onboard aircraft, less of the cabin air was recycled and more was fresh. However, the process of pressurising the fresh outside air and cooling it to cabin temperature requires more energy the recycling the existing air. So many operators have reduced the amount of fresh air and increased the amount of recycled air that is fed back into the cabin via the cabin environmental conditioning system.

Naturally the recycled air is passed through filters and cooled again by the air-conditioning system before being fad back in.

Happy to be corrected I was trying to be as simple as possible.

Sunny