We’ve found white noise works well for the baby, and helps me get back to sleep after the many night wakings too (Ewan front left foot is my favourite
).
I have noticed I quite often hear stuff behind the white noise if that makes sense. So one of the YouTube ones we use sounds like a choir singing, one on the machine sounds like some kind of chant etc. It’s all very repetitive and quite soothing but in the middle of the night I do sometimes worry it is brainwashing me into becoming a serial killer or something 
When I first turn it on or walk into the room it just sounds like white noise, also if I’m moving around but if I’m sat or lying still listening to it I can hear the other sound in the background.
Can anyone else hear it?? DP thinks I am nuts.