I don’t blame you for wanting some enclosure. Obviously those metal railings aren’t doing much for you. Are those acoustic panels high up near the ceiling?

I assume there’s no way to close the bottom of the stair?

Anything can be done with enough money thrown at it. Full walls to reach the soaring ceilings probably would be $$$$, but even freestanding 8’ or 10’ walls (to match the top of the inset behind the bed) might help a lot.

It is a gorgeous space for sure! The most obvious answer is to enclose the stairwell and installing a door at the top of the stair that opens into your bedroom. That's gonna be awkward since there is no landing. The International Residential Code requires a landing at both the top and bottom of a stair. So, you probably wouldn't be able to meet building code. If you were to be able to enclose the stairwell I might suggest opaque glass instead of wood framed walls. That way you should be able to keep natural light in the stairwell. Good luck!

What's at the bottom of the stairs? would enclosing/adding a door to the bottom of the stairs be feasible and decrease noise?

You would need to eliminate the winders, and take the stairs straight, which would run into the closet you built. Then build a wall. You would then need a 3x3 landing at the top, with a door into the bedroom. And you would then need to rent a crane to bring in any furniture, as only small things could navigate that and pivot to enter. Any other solution will involve relocating the stairs entirely, which would affect both floors. You will need an architect for that type of work. The other temporary alternative is to add heavy sound absorbing draperies all across that whole wall, and add an acoustic tile type treatment to the ceiling. That is not an inexpensive endeavor either, unfortunately.

Because the stairwell windows overlap the railing, there isn't a clear cut off point for a wall. A workaround is to extend the bedroom floor in front of them to create a nook for your dresser and where you'll also be able to add drapes for light control. That section will be high enough over the bottom winders to allow for headroom.

Instead of a solid wall where the railings are now, you could consider a double stacking sliding door system behind rails. You won't have worry about door swing, the bedroom door would stack over another door when open, then slide to close. All four doors (or panels) can slide open and stack on one end when you want it mostly open to move furniture and all four can slide across to make a solid wall. I'm not a fan of dark stairwells and would be inclined to use glass but you know what would best fit your needs. There are many options for doors and panels.

Can we see the bottom of the staircase please . I can't see how this will be accomplished with what you have going on at the top. This will require a ton of work and not be very attractive. What kind of noise is the issue?

This might be a dumb idea, but I’ll throw it out just in case. Could you just enclose the stairway almost like a tunnel with a door at the end? The ceiling over the stairs could be angled with the staircase or very high at the bottom to 8 feet or whatever you want at the top (so the tunnel is flat on top). Not sure what this would look like from the bedroom, but maybe you could turn it into a feature with a contrasting paint color or art. If the tunnel is flat on top, I guess it could be a large shelf, but that sounds kind of 80’s.

OK, that is a dumb idea but I can’t figure out how to delete my post in the app! Sorry!

Any idea can spark new thoughts., blueskysunnyday!

There's a natural place to build a wall--it's inside the railing, where the existing bedroom wall has been notched out for the stairs. The staircase even has some lovely windows. You'll need more art for the new wall.

Filling in the wall--without adding a door--should help with the sound a lot.

A landing is not required at the top of an interior flight of stairs, as long as a door does not open over the stairway. See IRC R311.7.6.

You will want one, though, to not have to simultaneously negotiate both the winder with your feet and lockset with your hands. You will also have some details to work out, like avoiding cover of the 5-gang switch center, the high wall register, how a deep landing might put the door wall under the high ceiling, how close the long wall would encroach on the stair windows without looking odd, and actually removing the railings and patching the floors or replacing with another finish if becoming a shelf.

What about these steps:

1. Remove the new closet
2. Straighten the stairs so they go into the space of new closet you built (where the two smaller old closets were)
3. build a wall where the stairs are
4. for the storage you need, do a wall of built-in wardrobes along the new wall enclosing the stairs and move the door to the bathroom to where the windows 1st old closet was so that you can put a closet in that corner where the current bathroom door is. Your bedroom is quite large so you have plenty of space for those two new closets.