That's what I'm looking for. I fancy recording a set of my own but my experiments haven't gotten the desired "intercom" attenuated sound. If anyone is familiar with Audacity (great free sound editing program) and wants to share the trick, I'd appreciate it. (If I get a good set I would be happy to share, too.) I'm looking for something that sounds like the Captain Sim announcements, or Simsounds. (I wonder if devs think English spoken with a BBC accent is fine for American domestic flights?) Thanks in advance.

I have found that the steps in this tutorial produce a very satisfying result:

I usually apply them twice, depending on the quality and perspective of the original audio file.

Additionally, this YouTube channel has plenty of high-quality recordings from a wealth of flights and airlines, usually from pre-boarding in the terminal until after landing or shutdown at the gate.

https://www.youtube.com/user/CourierPochi/videos