Best one thats free & no ads in my version

I downloaded about 6 different binaural sound apps this one is the best. In order for this to work you have to have headphones!
2nd app on my list is iMeditate thats if you like the sounds of munks praying. I think its cool but too distracting for me.
This app has 2 required features that not all apps had.
Best feature is to automatically adjust the frequency to a final slower frequency.
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This could be achieved quickly or slowly, you pick.
<< I usually set it to 10 min.>
2nd feature is to basically stop after a certain amount of time.
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**Initially you have to find the sound that tickles your brain (should be high frequency since youre awake & everyday will be different), then the freq. as it slows down will gradually make your brain slow down too.
Funny thing is that I wake up as if I had a really good sleep each time. No head aches! Im glad I didnt spent $200 on a beanie with headphones & brain wave sensor. Because this free app works.