I was told in a conversation w/ a glass installer that two panes w/ an airspace and a sound deadening film perform well. The larger the airspace the better. Laminated wasn't mentioned so you might inquire at a reputable glass shop about the air space method and get their thoughts and comparisons.

We made our own interior transoms, but weren't worried about sound insulation so can't help you with making your own insulated glass. I do have some ideas though. To frost glass, all you do is sandblast it (you can do it chemically too, but I'm not familiar with that process). You could buy a clear glass insulated unit and then have someone sandblast it for you. We have a neighbor that does it and he sandblasted a design onto the glass for our transoms, although we ended up not using it because we decided we wanted the whole window to be frosted. If you don't know anyone who does that, then ask a local glass company (not a building supply company where you buy the windows for construction, but a glass company) as I know that most of them do custom sandblasting/frosting of windows--we have them in my office. The other idea, if you are concerned about condensation between the two pieces of glass, is to construct it with one pane being like a removable storm window so that you could remove it and clean between the glass.

Wonder how acrylic blocks would work in this context-- might not be the look for every home, though.

I've considered transoms between the guest rooms and halls in my walkout basement, but I'm not sure if people would like it. People in the hall would know when lights were on in the rooms, and vice versa.

Just food for thought if you plan to use any tempered glass. I had a friend try to sand blast his tempered glass door and it shattered. I think the chemical method would have worked fine as well.
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I want to thank everyone for the replies so far, as always great information!