Aircraft noise attenuation calculations

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Bird on a Fire
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Re: Aircraft noise attenuation calculations

Post by Bird on a Fire » Wed Jun 24, 2020 11:20 am

Matatouille wrote:
Tue Jun 23, 2020 3:32 pm
Bird on a Fire wrote:
Tue Jun 23, 2020 11:36 am
I've digitised the figure from the EIA (it's for a proposed new airport, rather than the current one):
airport.png

The yellow polygon is their 65 dB area. The red boundary is an SPA, so EU-level protected area. The blue X is the proposed airport location, and the blue polygon is a wetland complex that was created as mitigation for the last infrastructure project that impacted these wetlands (Vasco da Gama bridge).
Yes that is definitely a landing sound profile, takeoff ones concentrate much closer to the airport, and tend to veer off in specific directions as they can direct jets onto egress headings that do most noise abating for the neighbours.

I think I've found a noise plot that they've done including your 65dB plot above, but also 55db, 60dB, and 70dB lines which might save you some work.
download link, I found it here. Open the pdf and go to page pdf page 106 (marked page number 102). It looks like the exact same plot for 65dB as in your map, so you might be able to translate the 50dB and 60dB lines onto a background more useful for your case of seeing how much of which wetlands are affected. It is then a matter of finding what assumptions they made for this - aircraft type, loading, glide angle etc and see if they hold up. I'm trying to get a copy of this pdf small enough that I can feed it into a translator because I'm lazy.
Bird on a Fire wrote:
Tue Jun 23, 2020 11:36 am
Some info is given about their assumptions in the EIA (in Portuguese - my translation):
1. Landing: From 1800m altitude and about 44 km from the runway. Less sound emission because the aircraft is reducing speed.
2. Landing [maintain altitude and landing gear): From about 800m of altitude and about 15km from the runway, and typically before about 9km distance from the runway, until landing. Greater sound emission, due to the use of flaps and power to maintain altitude and release landing gear.
3. Landing (reverse thrust): About 400m after touchdown. Even greater sound emission, due to the use of reverse thrust which helps decelerate the plane after touching down.
However, these are just generic figures taken from ANP (Aircraft Noise and Performance) for a Boeing 737-800 and the document “Civil Aviation Authority – Managing Aviation Noise. 2014”. I don't know if specific plans for runway operations were taken into account for their analysis.
Cheers, that is helpful. I'll do a bit more snooping about on this stuff.
Thanks Matt - that's absolutely perfect for my purposes.

I've been working on the EIA since last August, but hadn't thought to check that document (the final judgement from the commission in charge of the evaluation) for different plots.

It's quite interesting in that it acknowledges a lot of the problems with the EIA that we pointed out in our submission (eg that the data they used is 15 years out of date, that they massively underestimate the strength and scale of impacts, and so on) but then they go on to say that they're happy for the project to go ahead with some mitigation measures based on the figures from the EIA that they've just said are sh.t. (It's a matter of public record that the technical staff recommended rejecting the proposal, but were overruled by the politicians heading up the agency).
now I'm falling asleep and she's calling acab

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