I sometimes use SimplyNoise to have brown noise for sleeping or filter out distracting sounds in the office.

Also, iOS has background (white noise etc) sounds built-in: https://support.apple.com/en-us/109346 Android has something similar too?

We also installed triple-layered windows for sound insulation, but I believe it degraded the quality of the air, so sometimes have to open the windows for a few minutes before sleep to get fresh air.