Hi, I’m looking for feedback on the following hare-brained scheme:
I want to build a very cheap single-panel door for a 28” opening. It doesn’t have to look great, and it only needs to last a year or two. The main objective is noise abatement.
Question #1:
I’ve gleaned that it’s typical to use poplar or a hardwood for the rails/stiles, but I’m such a cheapskate that I’m considering using fir. Is that completely stupid?
Question #2:
The existing jamb is 1-9/16” deep. Should I shoot for a 1-9/16” thick door, or some other thickness? Would 1-1/2” work (see question #3)
Question #3:
If 1-1/2” will work (see question #2), can I achieve this by laminating 2 ¾” (fir?) boards?
Question #4:
If the answer to #3 is “you’re out of your mind”, what is the best way to obtain stock of the required thickness?
Thanks!!

This has to be a joke.

No joke, just ignorant. I am, or was anyway, sincerely looking for advice. Not sure why you'd say assume this was a joke, but I guess that is just further proof of my ignorance. "Thanks" for the dismissive response, way to build community!
My new plan is to go with a reclaimed door and tweak it to fit. I found one for $10 at our local Habitat for Humanity "Restore" warehouse. It's a couple inches too short but I think I'll jury-rig some kind of extender to the bottom.

For what you are trying to do it sounds like you are on the right track. Since it's short term and doesn't even have to look good, then go with whatever you can find on a budget that will fit the space. For more noise reduction, you could add a layer of solid foam to the unseen side.

Thanks Jaybee

Paws up to you for finding a reclaimed door. I have found Habitat's Restore store to be a gem when looking for random items. We needed a rustic medicine cabinet for our bath and I wanted it to be framed and recessed. We went to Habitat looking for something else and stumbled over a medicine cabinet that was marked $25 and 50% off that and almost exactly what I was looking for. I sanded it down and refinished it and it looks wonderful. Total cost was under $20. If you've priced them lately, you know they can be 10x that. Good advice from Jaybee.

The thickness your are taking sounds good. Just look for the door, one which fits there as per your budget. You can also try some door frames which will reduce the noise.