How do I listen to just the background sounds?
To do so, just turn the Voice volume fader on the Listen screen all the way down.
The Hypnotic Booster, which is a special frequency of binaural beats, will induce your brainwaves into a frequency associated with meditation, so you can even use it as part of a mindfulness meditation practice.
In the Sleep Well app, the binaural beats (also known as the Sleep Booster) will induce your brainwaves into a frequency associated with deep sleep — perfect for those times you want a little extra help falling asleep, even without the voice audio.
Note that the booster is very powerful, and you should avoid listening to the booster audio while performing activities that require your full attention, such as driving — even if you have disabled the voice audio.