What is that high pitched screeching noise occasionaly heard in Virginia Square in Arlington VA?

I’m guessing lawyers being questioned on their billable hours, but I haven’t heard your noise, so I can’t say for certain.

Maybe if you can describe it in more detail, such as time of day, intensity and duration, direction, that sort of thing. “Screeching sound” can cover a pretty wide range. (You should have heard my sisters years ago when I would look at them in the car.)

Perhaps it is this

Here is the site of the manufacturer of the Mosquito Teen Repellant that includes examples of the sounds so you can compare to what you heard

Loudspeaker malfunction, perhaps.