I live very close to a major international airport. The noise of planes landing and taking off isn’t loud enough to bother my family except for certain dogs. When we foster or dog-sit dogs that are thunderphobic they treat the aircraft noise just like any other thunderstorm - they’re terrified. The odd thing that I bring before you all for some information or educated guesses is this:
On clear weather conditions there’s no problem at all. The dogs don’t seem to notice the noise any more than we do. However, in overcast conditions where the cloud cover is very low, that’s when the dogs freak out. Which then makes me notice it also. What I’ve noticed is that in overcast conditions, the aircraft noise seems to have longer duration and is a little bit louder. It’s also oddly “dispersed”, sort of a soft roar which sounds to my ears a lot like a strong wind through the trees. Still not enough to bother me, but it makes the dogs freak out.
Is this an accurate perception that the overcast weather conditions somehow trap the sound closer to the ground? Perhaps it echoes between the ground and the cloud cover and back again, which makes it sound like the sound lasts longer?
I think that you are correct about the overcast conditions ‘trapping’ the sound. I’ve lived within 10 miles of an airport most of my life. I was also an aircraft mechanic for over 20 years. I’ve noticed the same phenomena.
In humid air, it travels a bit faster too, but less than 1% faster.
I suspect the greater humidity of the air absorbs more noise. A blanket of fog at our home can make the roaring of Lake Michigan very quiet, and causes the distant highway noises to vanish completely.
When the weather is poor the nature of air traffic into a big airport changes. If you happen to live at the right (wrong?) place the difference in noise can be obvious.
On a nice sunny day when the airport is not traffic saturated they may be using several runways. When the weather goes down they reduce the number of landing runways. Thereby concentrating the traffic over one set of houses while eliminating it over others.
On a nice sunny day when the airport is not traffic saturated individual airplanes will maneuver as they choose to get aligned with the runway maybe 4-5 miles out. When the weather goes down aircraft get lined up more like 10-15 miles out. Thereby concentrating the traffic over one set of houses while eliminating it over others.
On a nice sunny day when the airport is not traffic saturated individual airplanes will glide at idle power towards the runway until 2-3 miles out, then apply power to maintain landing speed until touchdown. When the weather goes down aircraft get fully slowed and powered up more like 5-7 miles out. Thereby spraying louder noise over 3-5 more miles of suburbia. And since they’re going slower, the impact on any given house is not only louder, but longer.
As you can see, all three of these factors are mutually reinforcing. If your house happens to be in the right (wrong?) spot it all adds up.
I don’t have any science to support or dispute that the clouds themselves alter the nature of the sound transmission. No comment plus or minus on that one. Though as QtM says, thick fog, or especially a falling snow can really muffle ambient sounds.
Recall that part of the plot of the original non-spoof movie Airport was that the airport normally avoided landing over one particularly noise-activist suburb. Unless the winds were overwhelmingly in favor of having to use that runway for safety. Which was/is actually the case at the real world O’Hare, both back in the 1970s when the movie was made and still today.
In the movie of course the winds forced the airport to land over that suburb on that fateful night, leaving the airport manager to deal with a protest march in his terminal as well as a crippled jet making an emergency return in a blizzard. Cue ominous music.
Your dogs may be smart enough to have recognized that scary thunderstorms happen when the sky is overcast and dark. Two situations that reinforce each other. So when a dog hears a thunder-like noise, and the sky is also dark & overcast, the dog gets more scared, and reacts more.
I used to work very close to a major airport and walked or cycled to the office everyday right under final approach. It was very noticeably louder on overcast days when planes were just skimming the bottom of the clouds. I always just assumed that some of the sound was being reflected back by the density change between the two layers.
Ditto. I live about a mile from the local train station. Most days I’m totally unaware of the train, but on humid days we can hear the bell as it approaches the station.
True. But I suspect particulate matter in the air, such as actual water droplets as in fog and snowflake ice particles, act to dampen sound rather than enhance its transmission.
Not really. The standard procedure results in the same descent angle from several thousand feet down to touchdown, come rain or shine.
Back in Ye Olden Dayes there were procedures that involved dropping down to a low altitude 3-5 miles from the field then flying level while “feeling your way” up to the runway. That mostly went out in the late 80s although smaller slower aircraft still use that method, particularly at minor airports.
Probably not applicable to the OP just outside (I think) Washington DC.
Right, I’m near Dulles airport. Within about 2 miles of it, I think. I do know from obervation that I’m almost due north of one of the north-south runways, so depending on whether they’re having planes land or take off from that runway in which direction we get more or less noise at home.
I grew up in pea soup thick fog (central valley, California) so I’m familiar with how fog tends to muffle sounds. This is the complete opposite.
We’re currently fostering with the possibility of keeping a thunderphobic dog. We can handle thunderphobia but since this overcast-increasing-the-plane-noise is also apparently a big problem, that makes a small, localized problem into a larger, general problem. In other words, we can deal with his fear for the 4 - 8 summer thunderstorms we get, but adding another 20 or so (complete guess) overcast problem days over a year is probably asking too much from the little guy. Also, thunderstorms tend to be limited to a few hours, but overcast days can last for several days. He has to go potty more often than that. Making him live in a scary place just isn’t good for him.
See acoustic refraction: when upper layers of air are warmer than lower layers, sound propagating away from its source tends to get deflected downward, back toward the ground, in a long arc. Your use of the term “dispersed” is consistent with such phenomenon, i.e. the direction of the source is difficult to identify - because the sound is kind of raining down on you from the warm upper layers of the atmosphere instead of beaming to you directly from the real source.
That’s one theory, anyway. Refraction may be working in conjunction with (or maybe even instead of) altered traffic patterns.
And I’ve got a gale warning tonight for the lake. Waves 4 to 8 feet by tomorrow. Gusts to 35 knots. Fog/overcast won’t keep the lake quiet tonight. I think I’ll check it out from the hot tub. It’s 14 degrees, should be okay if I wear a hat.
Hot tub in cool weather is vastly better than hot tub in hot weather. I can’t say whether 14F is too much cool for however hot his tub is. But it sounds plausible. The key thing is to not have a very far dash to get back in the house when you’re done.
