Subliminal Talk

This is very basic question, but I don't know the answer.. is this already answered?

So, let's say I'm at home for some hours and I'm reading, writing, cleaning, or something, and I want to listen to a 5G sub (AM6) with max. efficiency. How should I do it?

I seem to remember that the ultrasonic tracks are more efficient because the volume of the ultrasonic track is higher than in the masked tracks? Trickling stream is better than Ocean surf, because the former has a higher subliminal track volume? Stereo effect is important, but no idea to what degree...

Would the order of efficiency be something like this:
1. Ultrasonic track with headphones (not recommended, because an accidental increase in the volume level could results in hearing damage)
2. Ultrasonic track with speakers in a good stereo setting
3. Masked track, preferably Trickling stream, with headphones
4. Masked track, pref TS, with speakers in a good stereo setting
5. Ultrasonic track with speakers in a bad stereo setting or in mono
6. Masked track, pref TS, with speakers in a bad stereo setting or in mono

Are these differences significant, or is it about the same for options 1 to 4?

1) Masked with headphone is the best
2) then ultrasonic with speaker
3) and masked with speaker
4) mono
I think there is no difference between trickling and ocean. it's just that for most people the ocean is just too volume changing all the time (I didn't find the right word to say it).

Actually that whole long question of mine could have been just "Is it more efficient to listen to a masked track with headphones OR ultrasonic track with stereo speakers?" Wondering whether strereo image is more important than subliminal track volume, maybe.. oh well, I'll listen to the masked tracks at a fairly high volume.

For some people a high volume will trigger resistance and a lower volume will be better for them.