OFv2

[CatMan]

Would it matter if I cannot hear it (the US) at all?

The question is...

Is there ultrasonic audio being produced by the earbuds?  If so, then you're almost certainly going to damage your ears at those volumes using earbuds.  If not, then you're listening to silence.

The question of whether you can hear it or not only matters in that sense, because if your earbuds are producing ultrasonic audio, then you can hear it.  Even if your conscious mind is unaware of that fact.  That is, in fact, how and why ultrasonic subliminals work.

Fab10 brings up a good point also, and using earbuds at those volumes with ultrasonic should be producing horrible tinnitus.  That makes me think you may have accidentally been saved by crappy bluetooth compression stripping out the subliminal audio entirely.

Also I dont fully understand this post.
When I turn it up to high volumes I hear it, so I assume that means it IS producing the US audio, but when I turn it down (4-6/15) i dont hear anything. Does that mean I need to turn it up so I can consciously hear it at least a little or is it ok that I dont really hear anything.

Sounds like they might be having trouble reproducing the signal, it's supposed to be "silent" always. Or that was too loud a volume selected and they distorted. Also make sure any EQ or other related settings are set to default/off, that can cause distortion etc. too.

Look at my previous post and test the buds with the IML file. It's a free download.

Whats EQ

Equaliser. Most apps have some version of it. You want to make sure it's at default/off. The rest of my two posts should help further.