Planes and Clouds

[NEOWatcher]

Ok; strange question (IMO).
I've noticed this before, but never really gave it any notice until now.

Is it my imagination, or do planes going through a cloud actually sound louder?

I can think of a few ideas, but I'm not sure how or if they apply.
1) the sound is "trapped", or buffered somehow between the ground and the cloud deck.
2) the water vapor transfers the sound better.
3) the increased water in the jet intake somehow affects performance.

[adapa]

Ok; strange question (IMO).
I've noticed this before, but never really gave it any notice until now.

Is it my imagination, or do planes going through a cloud actually sound louder?

I can think of a few ideas, but I'm not sure how or if they apply.
1) the sound is "trapped", or buffered somehow between the ground and the cloud deck.
2) the water vapor transfers the sound better.
3) the increased water in the jet intake somehow affects performance.

That's a good question.

Clouds are not made of water vapor but of tiny water droplets or ice crystals (cirrus clouds and contrails). However, I don't know if these have any discernible effect on the transmission of sound.

Some older jets actually used water injection to increase thrust for takeoff. This is because the water injection will increase the mass flow and therefore increase thrust. However, I do not believe that the water droplets in clouds will have any major effect on the mass flow.

[Jens]

Is it my imagination, or do planes going through a cloud actually sound louder?

Just out of curiosity, do you mean to a person on the ground, or to a person who is inside the plane? I assume you mean the former.

And then a question for people who know more about flying than I do. Do pilots sometimes apply more thrust when passing through cloud layers to make the plane more stable as it's coming in for landing?

[NEOWatcher]

Clouds are not made of water vapor but of tiny water droplets or ice crystals (cirrus clouds and contrails).

If I thought it through, of course it is. At that temperature and atmospheric pressure, it can't be evaporated.

Just out of curiosity, do you mean to a person on the ground, or to a person who is inside the plane? I assume you mean the former.

Yes; from the ground.

Do pilots sometimes apply more thrust when passing through cloud layers to make the plane more stable as it's coming in for landing?

Although I notice it when there's a low cloud deck and for low flying planes*, the direction doesn't always seem to indicate a takeoff or landing on any airport too close.

*(wild guess: probably up to around 15-20,000ft)

[trinitree88]

Sound travels at different speeds in fluids of different densities....giving submarines a hiding place from sonar during WW2 when they found a temperature gradient. According to this, from clouds it can reflect too...SEE:http://books.google.com/books?id=3Qd...clouds&f=false

[Trebuchet]

As it happens, just yesterday afternoon I watched a pair of FA-18's passing over my house. They split up, one turning right, presumably heading for a landing at Whidbey Is. NAS, the other continued straight through a cloud. I noticed it seemed distinctly quieter through the cloud and got louder on emerging through the other side.

[Larry Jacks]

Is it my imagination, or do planes going through a cloud actually sound louder?

I can think of a few ideas, but I'm not sure how or if they apply.
1) the sound is "trapped", or buffered somehow between the ground and the cloud deck.
2) the water vapor transfers the sound better.
3) the increased water in the jet intake somehow affects performance.

Sounds like a good Mythbusters episode. First, there's the question of whether or not planes are louder when flying through clouds. If they're not, then end of problem. If they are louder, then it would be time to test various ideas as to why.

[Swift]

Although I notice it when there's a low cloud deck and for low flying planes*, the direction doesn't always seem to indicate a takeoff or landing on any airport too close.

*(wild guess: probably up to around 15-20,000ft)

I wonder if the low cloud deck is the key thing. Maybe, given a fairly uniform and low cloud deck, the sound gets sort of "trapped" between the cloud deck and the ground and gets amplified a little (this is all wild speculation). Or maybe the low cloud deck is just masking other background sounds. I have certainly noticed that the ambient noise level is lower in fog or in a snowstorm, I assume because the droplets of water or snowflakes are dampening the sound.

[Argos]

Interesting OP questions. I´ve never noticed that effect, but I´d guess that the sound in a cloud tends to be attenuated via absorption/scattering.

[NEOWatcher]

Sound travels at different speeds in fluids of different densities....

Could be. At first, I passed off the thought of the different densities because I would think that the higher density would "stay up there". But; given things like inversions, I guess I was too quick to pass it off.

I guess that might strengthen the idea of an echo (cloud to ground, back up, and return). Just like the echo of a duck's quack, it's hard to differentiate an echo of a jet exhaust.

... the other continued straight through a cloud. I noticed it seemed distinctly quieter through the cloud and got louder on emerging through the other side.

It might be the type of cloud too. Just like Swift said...

I wonder if the low cloud deck is the key thing...

...I usually notice it with rainy, or dreary low cloud deck conditions.

Sounds like a good Mythbusters episode...

I can see it now, another one of those episodes when Jamie and Adam are shown passing the time waiting for the conditions to be just right.

Or maybe the low cloud deck is just masking other background sounds.

Possibly, but to me it does sound much louder than nearby noises than at other times.

[slang]

Sounds like a good Mythbusters episode. First, there's the question of whether or not planes are louder when flying through clouds. If they're not, then end of problem. If they are louder, then it would be time to test various ideas as to why.

And no matter what, they will test how loud explosions sound in and outside clouds. Because explosions are science. And fun.

[flynjack1]

I have a question. Under what conditions did you notice this happening? Were you near an airport with low cloud conditions or were you noticing it with higher flying traffic? What were the wind conditions at the time. Wind on the ground has a huge influence on the sound reaching observers. As far as performance changes when flying through clouds, there are none needed, unless the temperature is at or below 5 degrees Celsius. When flying in clouds with cold temps, anti icing measures are taken but it would have no noticeable impact or overall aircraft noise.

If you were near an airport in low cloud conditions and an aircraft missed its approach he would throttle up for the missed approach and that would be a noticeable increase in noise.

[NEOWatcher]

Were you near an airport...

A little more than 15 miles, and perpendicular to the usual runway. The alternate runway approach would still be about 3 miles away.

... with low cloud conditions or were you noticing it with higher flying traffic?

Low heavy clouds. Not sure of the traffic height.

... What were the wind conditions at the time.

I'll have to mentally note that next time.

...Wind on the ground has a huge influence on the sound reaching observers.

I would also suspect winds at altitude based on clouds.

...If you were near an airport in low cloud conditions and an aircraft missed its approach he would throttle up for the missed approach and that would be a noticeable increase in noise.

No, not that. The frequency of the sound seems to be the same. Just the volume changes.

[flynjack1]

Curious, I have never observed this but after years of being around aircraft my hearing isn't the best. It would be intuitive to me that the denser the air the better the sound propagating properties. Sound does not propagate in space at least at human detectable levels. Heavy dense(aka moist low altitude) air should be more efficient than high altitude dry air, but whether these differences are detectable at livable elevations where people and airplanes coexist is the question. This should be calculable for some of the folks on this forum, but above my skills I'm afraid.

[mugaliens]

Curious, I have never observed this but after years of being around aircraft my hearing isn't the best. It would be intuitive to me that the denser the air the better the sound propagating properties. Sound does not propagate in space at least at human detectable levels. Heavy dense(aka moist low altitude) air should be more efficient than high altitude dry air, but whether these differences are detectable at livable elevations where people and airplanes coexist is the question. This should be calculable for some of the folks on this forum, but above my skills I'm afraid.

(sigh) get your hearing profile on records asap so post-retirement the hearing aids are covered for what you lost during military service. Establish that profile! If you're still flying, you've got the annual exam. Don't try to fudge it - just be honest. They won't (shouldn't) yank your flying status, but rather, will simply update your hearing profile.

And, oh, this is kid's stuff, but always use the yellow plugs and turn up the volume to compensate. I learned that the 9db loss the hard way.

[flynjack1]

Mugs, Long track record of hearing test results, but I havent attempted to get any benefits for the losses. I use noise reduction headsets these days....very nice, wish I had them when I was flying helos. Fortunately the FAA only requires conversational hearing range!