Why do planes have two engine noises?

[eyeshade]

I have noticed over the years that when planes fly over my house (and I live between 3 airports) they are quite quiet during the nightime hours but during the day the noise is up again, why is that? And why then don't they use the quieter engines during the day so that life would be more better than one flying directly over my head every 45 seconds!!

[Catso]

There could be loads of reasons why they seem different. A few could be:

They are just being considerate by keeping quiet at night.

It could be a condition of operating at night that they have to limit the noise.

They could be using slightly different flightpaths, different angles of climb, different power.

Different types of aircraft are used at night (EG more cargo flights). Different types have different noise levels.

[eyeshade]

The thing is, if they can be quiet at night, surely they could do it in the daytime?

[Catso]

In general terms, being quiet costs more money than being noisy. They probably can't afford it. Well, don't want to afford it.

[eyeshade]

That's more likely. I feel a letter coming on to the airport authority, I expect they'll that just at this moment!

[anotheoldgit]

A Turbo prop aircraft (cargo planes) makes much more noise than a Jet. It could be that Turbo props are banned from night flighing where you live they are not here the noisy devils.

[Garamond]

I always thought that planes were banned from taking off or landing between certain hours of the night.

[captken]

the air is more dence during day time therefore alows sound to travel at a further distance