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).
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Bird on a Fire
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Re: Aircraft noise attenuation calculations

Post by Bird on a Fire » Tue Aug 04, 2020 1:17 pm

We have an open access article out today explaining more about the pressures the noise from this proposed airport would create, not just on local wildlife but repercussing throughout the 'flyway' used by migratory birds: when heading from the Arctic to the Afrotropics they depend on a small number of key sites to refuel, and intense disturbance would hinder their feeding, with knock-on impacts on survival and reproduction.

Well worth a read for an insight into science-driven conservation: Perhaps the most prominent threat to waders in the East Atlantic Flyway.
At the end of January 2020, as migratory waders started to prepare for their northward journey to their breeding areas, the Portuguese Authority evaluating Environmental Impact Assessments (EIA) issued a favourable statement regarding the construction of a new commercial airport at the heart of the Tagus estuary, the most important wetland in Portugal for waders and other waterbirds.

Although imposing conditions (specifically, targeted com-pensation measures), this decision is a major blow to local and international conservation actions across the East Atlantic Flyway. Given the potential magnitude of the impacts and the high level of site-fidelity of species studied locally1,2, this new threat is likely to have important consequences for many of the already declining populations using the Tagus estuary3,4. Since reading the EIA for the first time in July 2019, we (including colleagues and fellow ‘waderologists’ concerned about this development) have embarked on a journey that is far from over.

<snip>

Technically, the proposed new airport infrastructure, which would expand the current capacity of, and operate in tandem with, the Lisbon airport, overlaps only slightly with the boundary of the Tagus estuary SPA. However, its location on the Montijo peninsula places it in the centre of this wetland, and aircraft would fly at low altitudes over parts of the SPA and Nature Reserve during approach and take-off (Fig. 1).
With thanks to Matatouille for help with Fig. 1! :D
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bmforre
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Re: Aircraft noise attenuation calculations

Post by bmforre » Tue Aug 04, 2020 5:05 pm

Thanks for posting this interesting informative material!

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Re: Aircraft noise attenuation calculations

Post by bmforre » Sun Aug 23, 2020 9:39 pm

Sensors to measure noise in air and on ground

Reported in Seattle Times by journalists working with flight-related matters.
Boeing and Etihad Airways have partnered to create the latest ecoDemonstrator, a new 787-10 Dreamliner built in South Carolina.

One of the tests involves 214 microphones (those circles connected with silver taping) on the fuselage. These are an innovative way to measure sources of noise on the aircraft and how the aircraft noise interacts and propagates to the ground.

The airframe noise tests are being conducted in partnership with NASA. An additional 1,000 microphones will be deployed on the ground at the testing site in Glasgow, Montana...
Hopefully this may improve future noise estimation.

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Re: Aircraft noise attenuation calculations

Post by Bird on a Fire » Thu Sep 17, 2020 10:58 pm

The story was published in a letter to Science today: https://science.sciencemag.org/content/369/6510/1440.1 It's technically paywalled, but you can read the whole piece in the "preview" image.

There's a lot going on behind the scenes. I'm going to start a thread on the topic when I'm less knackered - for now I'll just say thanks again for the help :)
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