Does brain state truly mirror entrainment frequency?

[tango]

I understand that each stage of LF includes a different frequency of entrainment. With this in mind, I have two related questions:

1) Is there any scientific evidence that shows to what extent the brain state of the person using LF actually mirrors the precise frequency of the particular stage to which they are listening? In other words, when a person is listening to LF 3 (for example), do their brain waves actually get to a frequency of 3Hz? Or is the effect less direct, so that a person using LF 3 will have brain waves that are generally lower than the same person using (for example) LF5, but not necessarily 3Hz?

2) If there is no evidence of the kind that I've described applying specifically to LF, is there any such evidence that applies to brain entrainment audio generally?

Thanks!