Something along these lines I recommend is a loud HEPA filter fan, so you get fresh air + white noise.

Currently living in China and this is a godsend

Use pink noise instead of white noise, if you can. It's less "sharp". Personally, I can't stand more than few moments of white noise, while I can listen to pink noise for hours (it reminds me of sea waves crashing into the shore).

Install sox and you might not need one. See my reply up-thread for details.