Off the top of my head, I think trained listeners can actually notice differences of 0.3 dB, though this sort of thing is going to be frequency dependent too.

But can they notice the difference on a random track, not on special test audio? Probably not.

Just play some music on your laptop/phone speakers and move the device around a bit, and you'll hear striking differences in highs and lows.

My laptop has speakers directed downwards, so putting a palm under it (to reflect sound upwards) increases the quality.