The sounds of leaves in wind during different seasons

[Delvo]

For as long as I can remember, I've noticed that leaves blowing in the wind have a different sound in autumn. The sound seems crisper or sharper, less soft or fluid, like I'm more distinctly hearing lots of impacts of tiny solid objects instead of hearing bending & flowing or getting all the impacts blurred together. At one time, I thought the main reason for the difference was probably just because when they're off the trees I'm hearing them repeatedly hit other objects instead of just hearing the sounds they'd make while still stuck on a tree. But I recently heard the familiar sound of autumn, coming entirely from up in the trees, which were mostly still green although with some yellow starting to sneak in. So what options does that leave me with, and have any of you ever heard of anybody having tried to scientifically check on any of them?...

1. The ones I heard in the trees were already detached and tumbling loose and hitting the branches but just hadn't worked their way all the way out yet so I didn't see them
2. It's not about detachment from the trees but about the loss of moisture, and the ones I heard in the trees recently had already had a bunch of their moisture extracted
3. The lower temperature of the air affects something about the transmission of sound from source to ear
4. It's all in my head; I'm feeling wind at a lower temperature than it's been in months, making the "autumn is here" association myself, and interpreting the sound as sounding like autumn
5. There's less other background noise at this time of year (from I don't know what sources because it's normally below the threshold to be consciously noticed & identified) for the details of this sound to get muddled by

?

[Jens]

For as long as I can remember, I've noticed that leaves blowing in the wind have a different sound in autumn. The sound seems crisper or sharper, less soft or fluid, like I'm more distinctly hearing lots of impacts of tiny solid objects instead of hearing bending & flowing or getting all the impacts blurred together. At one time, I thought the main reason for the difference was probably just because when they're off the trees I'm hearing them repeatedly hit other objects instead of just hearing the sounds they'd make while still stuck on a tree. But I recently heard the familiar sound of autumn, coming entirely from up in the trees, which were mostly still green although with some yellow starting to sneak in. So what options does that leave me with, and have any of you ever heard of anybody having tried to scientifically check on any of them?...

1. The ones I heard in the trees were already detached and tumbling loose and hitting the branches but just hadn't worked their way all the way out yet so I didn't see them
2. It's not about detachment from the trees but about the loss of moisture, and the ones I heard in the trees recently had already had a bunch of their moisture extracted
3. The lower temperature of the air affects something about the transmission of sound from source to ear
4. It's all in my head; I'm feeling wind at a lower temperature than it's been in months, making the "autumn is here" association myself, and interpreting the sound as sounding like autumn
5. There's less other background noise at this time of year (from I don't know what sources because it's normally below the threshold to be consciously noticed & identified) for the details of this sound to get muddled by

?

Interesting question, and it seems plausible, though I haven't really thought of it.

My guess would be that it's mostly 2, and perhaps a bit of 3, maybe less moisture in the air. It might also just be windier in the autumn.

[grant hutchison]

Shake a branch covered in green leaves; shake a branch covered in autumn leaves--they sound very different, with the autumnal branch producing a dry rattle.
As well as the dryness of the leaves, I'd suggest that another contributing factor to the characteristic sound is that autumn leaves are ready to drop, and are therefore less firmly held in position, so with the same applied force they're more likely to tap and rub against each other.

Grant Hutchison

[grant hutchison]

Oh, by the way: the word for the sound of wind passing through leaves is psithurism. I just thought you'd like to know that.

Grant Hutchison

[PetersCreek]

Oh, by the way: the word for the sound of wind passing through leaves is psithurism. I just thought you'd like to know that.

Grant Hutchison

I did, indeed.

[Squink]

Resorption of chlorophyll changes the texture and density of fall leaves, while the formation of a cork layer changes the stiffness of the stalk they hang from. Here. These alone are sufficient to produce changes in the sound of one leaf hitting another leaf, or a branch. Towards late October, you start to hear the even dryer sound of stick hitting stick.

[agassiz]

Cold brittle leaves, on or off the branch, will surely produce a sharper crisper "psithurism" when rattling against each other or other objects. Perhaps also, due to the weakened, brittle autumn leaf state, some psithurism would result from the tearing/ripping of leaves, which they would be more susceptible to in this season.