8 ms·

The map is a bit disingenuous for airports due to the metric used and the contours shown (out to the 35 LEQ contour?!). Federal Aviation Regulation Part 150 est

by knz 10y ago

The map is a bit disingenuous for airports due to the metric used and the contours shown (out to the 35 LEQ contour?!). Federal Aviation Regulation Part 150 established Ldn/DNL as the cumulative noise exposure metric for use in airport noise analyses and is used to determine mitigation eligibility (usually around the 65 DNL contour). I suspect there are more than a few people at the FAA and airports around the country who are not impressed that the U.S. Bureau of Transportation Statistics published this map. Community relations are hard enough without maps that use the wrong metric and show contours beyond a reasonable value in an urban area.

Anechoic 10y ago
For those of you that don't speak "noise control": Leq is the Equivalent Noise Level, is the energy of sound averaged over a set time period (usually an hour, the BTS site is doing it over 24 hours). Ldn/DNL is the Day-Night Noise Level. It's basically the same as a 24-hr Leq with one difference - 10 dB is added to noise levels generated between 10:00pm and 7:00am to account for increased/sleep sensitivity at night. My guess is that the site uses Leq because highway noise data is generally calculated using peak hour Leq and it was easier to get airport Leq data than to calculate highway Ldn data.
- knz 10y ago
  > My guess is that the site uses Leq because highway noise data is generally calculated using peak hour Leq and it was easier to get airport Leq data than to calculate highway Ldn data. Agreed. They should still know better than publishing something with contours out to 35 though! There is already a push by communities to mitigate aviation noise beyond the current level - 55 DNL is a number often thrown around and that often causes debate over ambient noise levels in an urban area etc. This map is going to cause headaches and confusion with the public.
  - mjevans 10y ago
    What I don't understand is why as a society we don't designate those areas non-residential to begin with. Beneath a flight path should be warehouse / industrial and possibly commercial.
    - dahart 10y ago
      Depends on which areas you're talking about specifically, but many major US airports did start that way. Lots of neighborhoods have grown into the flight paths, not the other way around. Why don't we keep it that way and protect bigger industrial boundaries around airports? I don't know, but it doesn't seem very realistic; it's too much prime land to control. Commercially zoned areas in every major metropolitan area have been approached, crowded, re-zoned or overtaken by residential development.

by knz 10y ago

Anechoic 10y ago

For those of you that don't speak "noise control": Leq is the Equivalent Noise Level, is the energy of sound averaged over a set time period (usually an hour, the BTS site is doing it over 24 hours). Ldn/DNL is the Day-Night Noise Level. It's basically the same as a 24-hr Leq with one difference - 10 dB is added to noise levels generated between 10:00pm and 7:00am to account for increased/sleep sensitivity at night. My guess is that the site uses Leq because highway noise data is generally calculated using peak hour Leq and it was easier to get airport Leq data than to calculate highway Ldn data.

knz 10y ago
> My guess is that the site uses Leq because highway noise data is generally calculated using peak hour Leq and it was easier to get airport Leq data than to calculate highway Ldn data. Agreed. They should still know better than publishing something with contours out to 35 though! There is already a push by communities to mitigate aviation noise beyond the current level - 55 DNL is a number often thrown around and that often causes debate over ambient noise levels in an urban area etc. This map is going to cause headaches and confusion with the public.
- mjevans 10y ago
  What I don't understand is why as a society we don't designate those areas non-residential to begin with. Beneath a flight path should be warehouse / industrial and possibly commercial.
  - dahart 10y ago
    Depends on which areas you're talking about specifically, but many major US airports did start that way. Lots of neighborhoods have grown into the flight paths, not the other way around. Why don't we keep it that way and protect bigger industrial boundaries around airports? I don't know, but it doesn't seem very realistic; it's too much prime land to control. Commercially zoned areas in every major metropolitan area have been approached, crowded, re-zoned or overtaken by residential development.