The alternative and using your ERR fatboy speaker concept- sounds like you want one unit per building or accessory.
I say this because there are MP3 "trigger boards" where they have a bunch of button inputs, you record sound files and name them in storage so they correspond to a button press, however the catch 22 is, one speaker output from the board. So the sound would not be localized to the building. Again, just such a board with multiple trigger inputs but only outputs to one speaker https://www.amazon.com/DEVMO-V...atible/dp/B09L4QM1PN
So if you want individual boards- one per building, this is the cheapest thing I know of and when bought in bulk, the price really goes down. This has a built in amplifier to connect to your ERR fatboy speaker. https://www.amazon.com/AITRIP-...coding/dp/B09DYBFHPL
Now, also, this could run off of the 4.5V typical Menards 5V building power. You also need to store the MP3 or audio on a USB stick or small microSD card (called a TF card in some countries). Also, these are not "trigger" boards and begin playing as soon as power is applied. A work around on that at our local club is we use arcade style big red buttons and a time delay relay board with multiple channels for controlling motorized action accessories. So, if an accessory was powered- then the sound module was powered kind of setup. Example for a sawmill, a button press fires the time delay relay channel, then an MP3 module is powered with sawmill sounds- but so is a smoke unit, lights, and action at the sawmill for a set time by the time delay relay module. Yes, more complicated, more parts- but we wanted all of our public actuated button based accessories on timers- so they start and run for several seconds or a fixed time rather than momentary.
8 channel time delay relay
Again, my point is, you can go as simple or as complicated as you want. You can have multiple boards, individual sounds and action from a building or you can have one speaker and common ambient sounds.
giant red arcade microswitch style lighted buttons