Noisy Planes Last Night

[Speedbird1]

I know that during bad weather the noise of aircraft are magnified. What exactly causes the noise to be louder? For example, last night we heard loud engines at 4000 feet approaching LGA Rwy 4. At other times, we don't hear the engines at all. What causes this? I believe it was snowing lightly at the time. I can also sometimes hear departures from 4L at JFK during stormy weather. Incidentally, I live in Sheepshead Bay.

[Gerard]

Low clouds?

[Derf]

I know that during bad weather the noise of aircraft are magnified. What exactly causes the noise to be louder? For example, last night we heard loud engines at 4000 feet approaching LGA Rwy 4. At other times, we don't hear the engines at all. What causes this? I believe it was snowing lightly at the time. I can also sometimes hear departures from 4L at JFK during stormy weather.

Reflective bass is the best kind... if you point your base speakers of a base tube forward in your trunk you will get less sound even tho the speaker are directing all sound foward. If you face them back towards the rear of the trunk, it will bounce forward and give you more punch. the closer to the back of the trunk, the tighter the bass will be, pull it more towards the front of the car (still in the trunk but with a bigger gap to the rear trunk lid) and you will get not as tight or muffled bass....people open the back seats and have the speaker facing into the cabin, are doing it all wrong.

If there is a ceiling or temp change, it will reflect most of the sound...snow sponges the sound and on a heavy fall it should be as quiet as it can be....

The more snow, the less noise

my .02 and may not be accurate but it is how I understand it.

[mirrodie]

Great thread.

I've noticed the same sort of noise amplification. I first noted it years ago with trains. Not on a snowy day, but on rainy day. Any rainy day, I could hear trains along the track (actually hear their wheels clacking across the switches) on any rainy day. And the trains were 5 miles away. But the sound carried much further during the rain.

As far as the loudness of planes, I think as stated the clouds play some role. I know when they use the 22s in poor wx, the jets come over our house at about 4000 feet and when they fly under the cloud cover, the sound is immense. But also, when they are low over the house but IN the clouds, the sounds is ALSO really magnified.

As Fred said, I think reflective bass plays a role, but I think perhaps also the fact that sound is partially traveling through a liquid medium may somehow play into it.

[Derf]

lifted from an airport website

.....Another weather condition that can affect noise transmission is a condition known as an inversion. This occurs when the air above is warmer than the air at the ground. This condition is opposite the norm, where the air gets colder as altitude increases. During an inversion, the noise that is directed up from the aircraft will ‘bounce’ off the warmer layer of air above and be re-directed back toward the ground.

http://www.msnairport.com/about/noise_faq.aspx

[Speedbird1]

Thanks for this interesting article Fred. I always knew that the weather had something to do with jet noise. I also think that the wind direction and velocity also affects the noise level. For example, on days with gale-force winds, I usually hear the engines at an increased decibel level.

[Delta777LR]

See, I live in Throgs Neck, I can actually sometimes hear the reverse thrusters loud enough that my walls vibrate sometimes

[Steven Holzinger]

I had two CH-53s flying over my house Tuesday night flying east at 10:36 PM and then heading in a westerly direction exactly one hour later. They were so friggen low and LOUD... couldn't be any more than 500 feet up. It's funny how any helicopter that flies over will rattle the windows... these guys REALLY rattled the windows!

I immediately called one of my friends who lives near NAS/JRB Willow Grove and told him there might be a CH-53 coming in and to listen to tower... surely, he told me "Hustler xx flight of two..." (I forget what the flight number was)

[Gerard]

[quote="mirrodie"]Great thread.
I've noticed the same sort of noise amplification. I first noted it years ago with trains. Not on a snowy day, but on rainy day. Any rainy day, I could hear trains along the track (actually hear their wheels clacking across the switches) on any rainy day. And the trains were 5 miles away. But the sound carried much further during the rain.
As far as the loudness of planes, I think as stated the clouds play some role. I know when they use the 22s in poor wx, the jets come over our house at about 4000 feet and when they fly under the cloud cover, the sound is immense. But also, when they are low over the house but IN the clouds, the sounds is ALSO really magnified.

Last night I went out into my backyard at 10:45 to let the dogs do their business and I heard a NCPD 407 landing at Bethpage which
is 4 miles from my house. Also could hear the swoop of traffic on 135. It was pretty clear last night and not cold but the ground still
cold from the snow.