Ask HN: How can I calculate how loud (dB) is a place/area?

Dear HN, I'm wondering if you can give me a hint how to calculate how loud is the place am living?

I live in Germany and my idea to build a tool where I can enter my address and find out the decibel number (day and night) based on the proximities to roads, airports, trains, etc, etc

Not sure if there is already any API or projects to get this in Europe (specially in Germany)

Thank you and happy holidays,