04-22-2020, 04:37 AM
To number 5, you have to test it out for yourself. A few years ago I didn't hear anything while I was playing the ultrasonic one, but back then I was a hobby musician, so a lot of loud noises that corrupted my hearing. Now when I play the ultrasonic, I can hear the difference between the audio and the silences. I don't have trouble sleeping while listening to ultrasonic, but in total I prefer masked one, the trickling stream because I became used to it since I started. It's just a nice sound to fall asleep to. When I was on a break I was missing the trickling stream for sleeping 
