Ultrasonic Vs. Masked

[smiliegirl]

What is the difference between them besides that one is silent and the other one has ambient music?

[ronatello]

The silent one is ultrasonic... it has a very high frequency signal around 15KHz. I like it because I can mix it in with music or have it play while I watch youtube clips, or TV.
The proper way to set the volume while listening to the ultrasonic is to play music on the speakers at the volume you normally listen to. Take note of the volume level and set it at that level when playing the ultrasonic versions.
The masked one contains ocean waves and if one listens close, one can barely hear the masked voices in between the waves as they increase / decrease in volume.

[Spiral]

When playing the masked just make sure you can here the softest part of the waves. You don't really actually have to HEAR the voices though.. I keep those sounds at a comfortable level and I cant hear the voices.. but when It gets to the louder/heavier waves I can slightly hear the voices.. it's sorta creepy lol but I've been able to fall asleep with the masked playing through my earbuds when I've been traveling. Just be cautious because I will tell you you don't sleep as good playing the masked ones. For me that was so but I was still able to rejuvinate my body's energy during my rest.