Hi there! I'll try to help you out:
1. Shannon has tested ultrasonics in a concert environment blaring very loud music. All heard the instructions several feet away and were seen to obey the script. So as long as your bedroom is quieter than a concert while sleeping, you should be fine lol.
2. Measure with Frequensee on your phone, I aim for -50db at middle of the bed.
3. Likely random. I wouldn't rely on headphones while sleeping unless you use something Sleepphones. It's too likely for the headphones/ear buds to fall off while sleeping, thus ruining the entire listening session as you won't know WHEN it fell out, and will have to throw out the whole night's hours. Use either Sleephones or speakers for best effect.
1. Shannon has tested ultrasonics in a concert environment blaring very loud music. All heard the instructions several feet away and were seen to obey the script. So as long as your bedroom is quieter than a concert while sleeping, you should be fine lol.
2. Measure with Frequensee on your phone, I aim for -50db at middle of the bed.
3. Likely random. I wouldn't rely on headphones while sleeping unless you use something Sleepphones. It's too likely for the headphones/ear buds to fall off while sleeping, thus ruining the entire listening session as you won't know WHEN it fell out, and will have to throw out the whole night's hours. Use either Sleephones or speakers for best effect.