Loud environmental noise can lead to serious negative health impacts. An example of this is aircraft flying overhead communities living around Dublin airport, writes Eoin King of University of Galway.

Lately, these residents have been making a lot of noise about noise. But they are living beside an airport – so what did they expect?

It turns out it is more complicated than that. Indeed, this is an issue which has led to much controversy in recent weeks, including a row between Ryanair boss Michael OLeary and transport minister Eamon Ryan (the pair met for the very first time recently). There are three issues at play here and all are causing concern for residents.

What is the issue with flight paths?

It goes back to 2007 when daa got planning permission to build the new North Runway. As part of the planning application, an environmental impact assessment was undertaken to evaluate the impact on all environmental factors, including noise. Predictions were made to determine how much noise would come from the planes using this new runway, and which communities would be affected.

On the back of these predictions, many residents (and some schools and pre-schools) were eligible to receive noise insulation to reduce the impact. Fingal County Council also developed noise zones which restricted new residential development in areas that would be under the flight paths from aircraft using the new runway.

Fast forward to 2022 and the North Runway opened 15 years after planning was granted. It turns out that planes are now flying over entirely different houses than were planned for. This means that houses that were never meant to be flown over now find themselves directly under a flight path – including new houses that were built recently in the area.

When these new houses were built, they were given planning permission to be built, as the noise predictions showed that they would not be impacted by noise at all (in fact the flight path should have been up to 5km away in some cases!).

It is a pretty straightforward problem: planes are now flying directly over houses that were not part of the assessment when planning was granted. 

What about night-time noise?

When planning was granted in 2007, it was subject to certain conditions. One condition sets a limit on the average number of night-time flights at 65 per night. At that time, there were about 40 flights a night in Dublin airport, so the limit of 65 was chosen as it allowed the airport to expand its operations at night-time, but also balance the impact of noise on residents.

But today, there are more than 100 flights a night at Dublin airport. So how did this happen? The limit of 65 only kicked in when the North Runway opened.

Because this limit has been exceeded (by almost double), last year, Fingal County Council issued an enforcement order against daa, though the High Court later granted a stay on this enforcement order. daa are now seeking to have this night-time flight limit replaced with a Noise Quota System, and this is being considered by An Bord Pleanála.

What is the noise quota system?

The proposed Noise Quota System allocates a certain number of noise 'points' for the night-time period across the year. The scheme is proposed to encourage airlines to introduce quieter planes because they take up less of the allocated noise budget. It is based on a similar scheme used in HeathrowGatwick and Stansted airports. 

However, there is one big difference. The London airports include a movement limit (ie a limit on the overall number of flights throughout the night) as well as the noise quota.

Heathrow has a night-time limit of about 20, compared to Dublin’s 65 (the limit that daa want dropped). As well as that, the quota that is proposed for Dublin far exceeds those airports in London, so, with a high quota, and no movement limit, the proposed quota system is unlikely to lead to any noise reduction.

What about the passenger cap?

There is currently a limit of 32 million passengers at Dublin airport, but daa would like this increased to 40 million. While this passenger cap is not related to noise, raising the cap will obviously have a significant impact on noise levels.

Simply put, more planes in the sky means more noise. Yes, aircraft are slightly quieter now than they were years ago, but there are many more planes in the sky which means aircraft noise is actually going up: daa’s airport noise monitors show that noise has been steadily increasing since 2017. 

So what can be done?

Technological solutions are making planes quieter, but we are years away from the type of significant reductions that would have a meaningful impact even with these advances. Discussions around quieter planes, land use planning, noise quotas, etc, will not help anybody today.

Nobody is arguing for zero noise and the noise from the airport was accounted for in the planning permission for the North Runway, but the plans that were set out in 2007 are not being implemented today.

The easiest solution would be for the airport to operate as envisioned in the original planning application. As for the passenger cap: more passengers mean more flights and no end to the daily and nightly impact of these flights on noise levels in communities around Dublin airport.

Author: Dr Eoin King, director of the Galway Sound Lab and a lecturer and programme director of mechanical engineering, at the University of Galway This article first appeared on RTE Brainstorm.