Carpet the stairs.

Julie, change your account so I can send a private message, I can recommend a contractor in San Diego who might take a small job.

Where exactly do you think a door will fit/ IMO try to be quiet in the AM . This shoulf have been dealt with durung the reno since privacy in a master bedroom is a big issue .

we have a door upstairs. a door can fit, its a 38” width 46” depth and 8’ height. we didnt know sound would be an issue. we cant keep the master bedroom door closed ar night, our cats would keep us awake. I am quiet in the mornings. Can only make coffee with the kurig, god forbid I out a pan on the stove to cook an egg or set a bowl on the counter for some ceral without making the slightest knick of a sound.

Have you tried a sound machine or app?

What is the sound problem? You walking around the kitchen in sneakers? Or talking on zoom calls? If the sounds to buffer are fairly minor and it's an echo problem, more fabric will help. Curtains for the stair window, carpet for the steps, quilt as decor on the wall, etc.

You could always put a cat door in the master BR door. An interior wood door should be easy to modify. You can buy a cat door or make an attractive one. A hole and a flap should do. You don't have to worry about mice, skunks or other critters getting in or the heat esacping.

I would try a textured decorative screen that you can fold up and store during the day. Leave a little room on one side for the cats to come and go.

Put a doggy door on your bedroom door.

That is actually not a terrible idea

You can add seals around the frame and a sweep on the door bottom.

Have your husband start work at 7am.

(humor)

When mrs. worthy insists on a 5:30 AM start on her day, I roll over and embrace the sounds of silence.

(not humour)

Hello darkness my old friend.

There are other variations of cat doors. I googled cat door for door.

https://www.amazon.com/Purrfect-Portal-Interior-Cat-Door/dp/B08LP287J4/ref=asc_df_B08LP287J4/?tag=hyprod-20&linkCode=df0&hvadid=475826503085&hvpos=&hvnetw=g&hvrand=3569735222738193102&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9019695&hvtargid=pla-1209061177135&psc=1&mcid=d035097d22a136529926d937220a1a83&gclid=Cj0KCQiArrCvBhCNARIsAOkAGcWSyTM0aZA5oL_V4Twc8hgzljSM_b1f8JE3KxObu6IjphJm5Tq-5OUaAueFEALw_wcB

During your reno what did you do that made things suddenly loud? What changed? Carpet?

My solution to the cats is a door at the bottom of the stairs with the cats down there. This is partly humor and partly just the truth. We built with a relatively open stairwell and now we have to put the cats outside or sleep is interrupted. For some reason, my wife stresses about them getting cold out there when it is 35 or less. I am understanding for the few nights below 25. But they were born outside and survived as new born kittens although to be fair it was springtime. But their parents did ok.

I would build a door at the bottom of the stairs. The cat door would help of course but having to be quiet is really annoying - I'm the early riser. I am a big fan of 2 doors to separate public space from primary bedroom. But you need to decide which side the cats are on unless you leave the bottom open at night and they come down with you.

As a temporary solution, hang a heavy fabric (woven jacquard is a good option) on a closet rod across the opening (easy to mount brackets and a dowel) that you can tie back during the day or drop to cover the door during sleeping hours. I did this to stop heat from gas logs rushing up a stairwell and my four cats could easily slip by the sides of the dropped curtain. It might block some sound while you figure out the big fix or the cats "age out."

There are apparently sound deadening curtains…. Try search audio curtains.

Cat door + sound machine will probably be a great combo.

I know this may not work for everyone but i use earplugs. I had to try a few different tyoes but really is a lifesaver. My husband comes in at 2am and makes a ruckus. The plugs are just enough to sleep though that but hear the alarm at 5:30 am.