This is already known data, you simulate the conditions of the womb and a baby in the 4th trimester (we're born early because of our big heads), will sleep easily. So swaddling, swaying and shhhing all simulate being in the womb where you hear white noise, are tightly confined and gently rocked or swayed by the mother's natural movement as she walks around, etc.

I read about it with my own children and it worked, and there was science behind it. https://www.happiestbaby.com/blogs/baby/the-5-s-s-for-soothi...