The World Health Organization says that to sleep properly, the noise in your bedroom at night should stay under 30 decibels.
But nobody measures inside your bedroom. So you work out how loud it can be outside, and that depends on one thing: is your window open or shut?
In 2020 daa’s noise consultants did the sum both ways, in the same paragraph.
Window open, using a figure they sourced to the WHO: the outside limit is 45 decibels.
Window closed, “assuming” a figure they sourced to nothing: 55 decibels.
Ten decibels is a lot. To the ear, roughly twice as loud.
Which one did they use to decide whether a night’s noise counts as a significant impact? The 55. “Adopted here as a threshold for significant impacts”, based on “an assumption of closed windows.”
Remember the open window. It does come back.
In the same report, when counting how many times a night a plane is loud enough to disturb your sleep, they used the window “slightly open”. That count, the report says, has “no conventionally accepted method” for assessing impacts. So it decides nothing.
And the WHO? In its own night noise guidelines it explains why a figure that covers the whole year can’t assume shut windows, because “even in well-insulated houses windows may be open a large part of the year”. Its health-based guideline outside is 40 decibels. 55 is its fallback for places that can’t manage that yet, and it says, in terms, that 55 “is not a health-based limit value by itself”.
So, here’s where we’ve landed. When they count how often you’re woken, your window is open. When they decide whether being woken matters, your window is shut. The organization they cite says your window is open a large part of the year, and that 55 isn’t a health-based limit by itself.
On paper, everybody at Dublin Airport sleeps with the window open and wakes up with it shut.
Sources
- World Health Organization, Guidelines for Community Noise, edited by B. Berglund, T. Lindvall and D. H. Schwela, Geneva, 1999 (the indoor guideline of 30 dB LAeq for sleep, which daa’s consultants cite as their starting point). WHO IRIS: https://iris.who.int/handle/10665/66217
- Bickerdike Allen Partners, Dublin Airport Aircraft Noise Methodology Report, prepared for daa plc, reference A11267_16_RP016_3.0, 31 March 2020 (the 45 dB window-open and 55 dB window-closed conversions in Appendix 2; the 55 dB “adopted here as a threshold for significant impacts” on “an assumption of closed windows”; the N60 count with the window “slightly open”; and “no conventionally accepted method” for the supplementary metrics). Submitted to the Aircraft Noise Competent Authority on Fingal County Council planning application F19A/0449 and published on the planning file (received 31 March 2020): https://planning.agileapplications.ie/fingal/application-details/85071
- World Health Organization Regional Office for Europe, Night Noise Guidelines for Europe, Copenhagen, 2009, ISBN 978 92 890 4173 7 (windows “may be open a large part of the year”; the night noise guideline of 40 dB Lnight, outside; the interim target of 55 dB, which “is not a health-based limit value by itself”). WHO IRIS: https://iris.who.int/handle/10665/326486