How can I generate a noisy environment to test my PCB?
If you can't afford a full-size EMC chamber you could consider a TEM cell (and maybe an EMC "bag").

It is basically a piece of waveguide that you can put small things in. It works both for measuring the emissions from your PCB (when connected to a spectrum analyzer) and for testing immunity (you connect an RF amplifier on one end and a dummy load on the other).

It looks like this:
https://www.telonic.co.uk/Tekbox-TBTC2-TEM-Cell-p/tbtc2.htm
https://www.emcfastpass.com/test-equipment/shop/gtem-tem-cells/compact-tem-cell-tbtc1/