This app was mentioned in 2 comments, with an average of 2.00 upvotes
https://play.google.com/store/apps/details?id=com.myniotech.noisewall&hl=en
and
https://play.google.com/store/apps/details?id=com.myniotech.noisewall_pro&hl=en
This noisemaker app has saved my sleep many times when I was without a fan.
https://play.google.com/store/apps/details?id=com.myniotech.noisewall