It depends a lot on the house, in my experience. Newer houses have it worse than older ones.
Older houses seem to have it better. But this is true of Semi-D houses, too. Ideally what you want is to look at the layout of the houses. Builders with common sense will lay all the houses out the same, so the front doors/stairs are all on the same side. Meaning no one's bedrooms are adjoining. Unfortunately, most Semi-Ds tend to do a mirror-image thing, which is woeful, and all the bedrooms adjoin. A mid-terrace can be a bit of a wildcard in this regard, so you should keep an eye on that.
I've lived for a long time in an 80s council, all block build (semi D) and our rooms are on the outer-side of the house, meaning silence. I lived recently in a 2010-ish build semi D that did it the other way, and the staircases are at the outer-side, meaning all bedrooms are adjoining. I could hear sex if it was particularly active, the baby cries, doors slamming etc. but it was never too bad.
The problem is it can vary from estate to estate. I was in a vacant house a couple of weeks ago and it was the worst I'd ever heard. I could hear a child walking around the room in the house next door, which was ridiculous.
There's no consistency, but if you're looking at older houses, chances are you'll be somewhat alright.