In a way, I wish that the government had put up noise level measuring equipment in every populated area of the country, allowing me to see on a map which areas are the most quiet and peaceful over time.

Sadly, this screams "surveillance nightmare" to me, as these devices probably would be, or could act as, microphones, and thus record the actual sounds/conversations rather than just checking the noise level.

Is it possible to make devices which only measure the noise level, but cannot record/pick up actual speech or human communication? And if so, are those cheaper than the microphones, or would they have to be specifically manufactured for more money? (And thus very likely not be done.)

Is this a "thing" which exists? Or would it have to be expensively invented and then have surveillance-prone people convinced to use them instead of microphones?